The difference between Srila Prabhupada's books and other so-called gurus' (conditioned souls) writing is Srila Prabhupada's instruction was coming directly from Krsna. This is the transcendental platform.
Srila Prabhupada encouraged his disciples, however, to write their realizations. Other conditioned souls may present their nonsense commentaries on Bhagavad-Gita etc., but they will NEVER be QUOTED FOR REFERENCES. Srila Prabhupada is on the TRANCENDANTAL platform and Krishna speaks through him, consequently ONLY he will be QUOTED FOR REFERENCE.
His Divine Grace Srila Prabhupada is always consulting Krsna:
Srila Prabhupada Interview, July 14, 1976, New York:
Bali-mardana: "In other words, when you decide that someone is to be in charge of a particular temple does Krsna tell you that this person should be in charge.
Interviewer: Or do you by judging him say this person is qualified.
Prabhupada: Yes, because a devotee always consults Krsna and He gives order.
Interviewer: It's a more direct communication.
Prabhupada: Yes. And He gives order.
Ramesvara: Because intelligence, our philosophy is that intelligence comes from Krsna. So if I have some...
Interviewer: And your philosophy is that your daily necessities come from Krsna as well.
Ramesvara: Yes, try to understand. Suppose my intelligence sees that this person is qualified, that means Krsna has told me.
Prabhupada: No, not necessarily, Krsna will tell directly. A devotee always consults Krsna and Krsna tells him, "do like this." Not figuratively. Interviewer: Does that apply then to other kinds of decisions and other kinds of activities as well?
Prabhupada: Everything. Because a devotee does not do anything without consulting Krsna."
His Divine Grace Srila Prabhupada speaks as Krsna speaks:
Caitanya-caritamrta Antya 5.71:
"One is forbidden to accept the guru, or spiritual master, as an ordinary human being (gurusu nara-matih). When Ramananda Raya spoke to Pradyumna Misra, Pradyumna Misra could understand that Ramananda Raya was not an ordinary human being. A spiritually advanced person who acts with authority, as the spiritual master, speaks as the Supreme Personality of Godhead dictates from within. Thus it is not he that is personally speaking. When a pure devotee or spiritual master speaks, what he says should be accepted as having been directly spoken by the Supreme Personality of Godhead in the parampara system."
The difference is Srila Prabhupada speaks what Krsna speaks and so-called gurus have to jog the brain to give answers.
Caitanya-caritamrta Adi 8.39 - The Author Receives the Orders of Krsna and Guru:
"It is not possible for a common man to write books on bhakti, for his writings will not be effective. He may be a very great scholar and expert in presenting literature in flowery language, but this is not at all helpful in understanding transcendental literature. Even if transcendental literature is written in faulty language, it is acceptable if it is written by a devotee, whereas so-called transcendental literature written by a mundane scholar, even if it is a very highly polished literary presentation, cannot be accepted. The secret in a devotee's writing is that when he writes about the pastimes of the lord, the lord helps him; he does not write himself. As stated in the Bhagavad-gita (10.10), dadami buddhi-yogam tam yena mam upayanti te. Since a devotee writes in service to the Lord, the Lord from within gives him so much intelligence that he sits down near the Lord and goes on writing books. Krsnadasa Kaviraja gosvami confirms that what Vrndavana dasa Thakura wrote was actually spoken by Lord Caitanya Mahaprabhu, and he simply repeated it. The same holds true for Sri Caitanya-caritamrta. Krsnadasa Kaviraja Gosvami wrote Sri Caitanya-caritamrta in his old age, in an invalid condition, but it is such a sublime scripture that Srila Bhaktisiddhanta Sarasvati Gosvami Maharaja used to say, "The time will come when the people of the world will learn Bengali to read Sri Caitanya-caritamrta." We are trying to present Sri Caitanya-caritamrta in English and do not know how successful it will be, but if one reads the original Caitanya-caritamrta in Bengali he will relish increasing ecstasy in devotional service."
Caitanya-caritamrta Adi 8.72 - The Author Receives the Orders of Krsna and Guru:
"To write about the transcendental pastimes of the Supreme Personality of Godhead is not an ordinary endeavor. Unless one is empowered by the higher authorities, or advanced devotees, one cannot write transcendental literature, for all such literature must be above suspicion, or, in other words, it must have none of the defects of conditioned souls, namely, mistakes, illusions, cheating and imperfect sense perceptions. The words of Krsna and the disciplic succession that carries the orders of Krsna are actually authoritative. To be empowered to write transcendental literature is a privilege in which a writer can take great pride. As a humble Vaisnava, Krsnadasa Kaviraja Gosvami, being thus empowered, felt very much ashamed that it was he who was to narrate the pastimes of Lord Caitanya Mahaprabhu."
Caitanya-caritamrta Adi 9.4 - The Tree of Devotional Service:
"This is the process for writing transcendental literature. A sentimentalist who has no Vaisnava qualifications cannot produce transcendental writings. There are many fools who consider krsna-lila to be a subject of art and write or paint pictures about the pastimes of Lord Krsna with the gopis, sometimes depicting them in a manner practically obscene. These fools take pleasure in material sense gratification, but one who wants to make advancement in spiritual life must scrupulously avoid their literature. Unless one is a servant of Krsna and the Vaisnavas, as Krsnadasa Kaviraja gosvami presents himself to be in offering respects to Lord Caitanya, his associates and his disciples, one should not attempt to write transcendental literature."
Srila Prabhupada Letter to Satsvarupa, February 28, 1972:
"You ask one question about the nature of books I want you to write as my disciples; on this point, Krsna Consciousness is not limited. Persons like all of the Gosvamis wrote so many books, Visvanatha Cakravarti, and all the acaryas wrote books, and still I am writing books. Similarly, also my disciples will write. So any self-realized soul can write unlimited books without deviating from the original ideas."
Caitanya-caritamrta Madhya 12.150 - The Cleansing of the Gundica Temple:
"This is a matter of etiquette. If a previous acarya has already written about something, there is no need to repeat it for personal sense gratification or to outdo the previous acarya. Unless there is some definite improvement, one should not repeat."
Srila Prabhupada Room Conversation, July 5, 1976:
Prabhupada: "brahma-sutra-padais caiva hetumadbhir viniscitaih. Very.... Nyaya-prasthana. But Vedanta-sutra is explained in Srimad-Bhagavatam. Therefore our gaudiya Vaisnavas, they did not write any comment on the vedanta-sutra. They accept Srimad-Bhagavatam is the real bhasya. But when the gaudiya-vaisnavas are challenged that "you have no vedanta-sutra-bhasya, therefore you cannot be accepted as transcendental party," so Baladeva Vidyabhusana immediately gave Govinda-Bhasya on vedanta. Our gosvamis, they did not write because they knew brahma-sutra bhasya, Srimad-Bhagavatam."
Caitanya-caritamrta Adi 9.5 - The Tree of Devotional Service:
"This is the sum and substance of transcendental writing. One must be an authorized Vaisnava, humble and pure. One should write transcendental literature to purify oneself, not for credit. By writing about the pastimes of the Lord, one associates with the Lord directly. One should not ambitiously think, "I shall become a great author. I shall be celebrated as a writer." These are material desires. One should attempt to write for self-purification. It may be published or it may not be published, but that does not matter. If one is actually sincere in writing, all his ambitions will be fulfilled. Whether one is known as a great author is incidental. One should not attempt to write transcendental literature for material name and fame."
Caitanya-caritamrta Adi 11.7 - The Expansions of Lord Nityananda:
"One should not write books or essays on transcendental subject matter for material name, fame or profit. Transcendental literature must be written under the direction of a superior authority because it is not meant for material purposes. If one tries to write under superior authority, he becomes purified. All Krsna conscious activities should be undertaken for personal purification (apana sodhite), not for material gain."
Caitanya-caritamrta Adi 14.1 - Lord Caitanya' s Childhood Pastimes:
"The author of Caitanya-caritamrta takes shelter of Lord Caitanya Mahaprabhu to describe the pastimes of His appearance as a child because one cannot write such transcendental literature by mental speculation. One who writes about the Supreme Personality of Godhead must be especially favored by the Lord. Simply by academic qualifications it is not possible to write such literature."
Caitanya-caritamrta Madhya 19.132 - Lord Sri Caitanya Mahaprabhu Instructs Srila Rupa Gosvami:
"Srila Rupa Gosvami and Sanatana Gosvami had no fixed residence. They stayed beneath a tree for one day only and wrote huge volumes of transcendental literature. They not only wrote books but chanted, danced, discussed Krsna and remembered Sri Caitanya Mahaprabhu's pastimes. Thus they executed devotional service.
In Vrndavana there are prakrta-sahajiyas who say that writing books or even touching books is taboo. For them, devotional service means being relieved from these activities. Whenever they are asked to hear a recitation of Vedic literature, they refuse, saying, "What business do we have reading or hearing transcendental literatures? They are meant for neophytes." They pose themselves to be too elevated to exert energy for reading, writing and hearing. However, pure devotees under the guidance of Srila Rupa Gosvami reject this sahajiya philosophy. It is certainly not good to write literature for money or reputation, but to write books and publish them for the enlightenment of the general populace is real service to the Lord. That was Srila Bhaktisiddhanta Sarasvati's opinion, and he specifically told his disciples to write books. He actually preferred to publish books rather than establish temples. Temple construction is meant for the general populace and neophyte devotees, but the business of advanced and empowered devotees is to write books, publish them and distribute them widely. According to Bhaktisiddhanta Sarasvati Thakura, distributing literature is like playing on a great mrdanga. Consequently we always request members of the International Society for Krishna Consciousness to publish as many books as possible and distribute them widely throughout the world. By thus following in the footsteps of Srila Rupa Gosvami, one can become a rupanuga devotee."
Caitanya-caritamrta Antya 1.211 - Srila Rupa Gosvami' s Second Meeting With the Lord:
"Unless one is a fully unalloyed devotee of the Lord, one should not try to describe the pastimes of Krsna in poetry, for it will be only mundane. There are many descriptions of Krsna's Bhagavad-gita written by persons whose consciousness is mundane and who are not qualified by pure devotion. Although they attempted to write transcendental literature, they could not fully engage even a single devotee in Krsna's service. Such literature is mundane, and therefore, as warned by Sri Sanatana Gosvami, one should not touch it."
Caitanya-caritamrta Antya 5.133 - How Pradyumna Misra Received Instructions from Ramananda Raya:
"Only if you follow the principles of Sri Caitanya Mahaprabhu and His devotees will your learning be successful. Then you will be able to write about the transcendental pastimes of Krsna without material contamination."
Srila Prabhupada's Lecture on Srimad Bhagavatam, August 21, 1972, Los Angeles:
"Uttama, uttama means udgata-tama. This material world is tama, ignorance, darkness. And Krsna is beyond this material world; therefore He is called para. Para means transcendental. So uttama-sloka. So when we offer our prayers to krsna, they are not ordinary words. Therefore those who are not liberated soul, they cannot offer prayers actually. we have to repeat the prayers offered by liberated soul, not by ordinary man. Because he is not yet uttama, he is not yet in the transcendental platform. Therefore we don't allow songs which are not sung by liberated souls like Bhaktivinoda Thakura, Narottama dasa Thakura. They are liberated souls. We don't allow any literature which is not given by liberated soul. Literatures, they are always following Vedic principles. Vedas, the original transcendental literature, and any literature which is produced under the guidance of Vedic literature, that is also nice. That is perfect. Therefore whenever we write something, we give immediately vedic evidence. We give some sanskrit verse. This means that we are not manufacturing ourself. What we have heard from the parampara system, from higher authorities, we are presenting, simply, in our own language, and the evidence is this Vedic verse. This is perfect literature."
Srila Prabhupada's Lecture on Srimad Bhagavatam, September 26, 1972, Los Angeles:
"So everything is there Srimad-Bhagavatam. That is the topmost knowledge. That is transcendental knowledge. That is not material knowledge. Material knowledge, if you write some book, it has no meaning, because it is defective. But Srimad-Bhagavatam is not ordinary knowledge. It is transcendental knowledge. There is no defect."
Srimad Bhagavatam 9.10.3 - The Pastimes of the Supreme Lord, Ramacandra:
srutam hi varnitam bhuri
tvaya sita-pater muhuh
tasya--of Him, the Supreme Personality of Godhead Lord Ramacandra and His brothers; anucaritam--transcendental activities; rajan--O King (Maharaja Pariksit); rsibhih--by great sages or saintly persons; tattva-darsibhih--by persons who know the Absolute Truth; srutam--have all been heard; hi--indeed; varnitam--as they have been so nicely described; bhuri--many; tvaya--by you; sita-pateh--of Lord Ramacandra, the husband of mother Sita; muhuh--more than often.
O King Pariksit, the transcendental activities of Lord Ramacandra have been described by great saintly persons who have seen the truth. Because you have heard again and again about Lord Ramacandra, the husband of mother Sita, I shall describe these activities only in brief. Please listen.
"Modern Raksasas, posing as educationally advanced merely because they have doctorates, have tried to prove that Lord Ramacandra is not the Supreme Personality of Godhead but an ordinary person. But those who are learned and spiritually advanced will never accept such notions; they will accept the descriptions of Lord Ramacandra and his activities only as presented by tattva-darsis, those who know the Absolute Truth. In Bhagavad-gita (4.34) the Supreme Personality of Godhead advises:
tad viddhi pranipatena
upadeksyanti te jnanam
"Just try to learn the truth by approaching a spiritual master. Inquire from him submissively and render service unto him. The self-realized soul can impart knowledge unto you because he has seen the truth." Unless one is tattva-darsi, in complete knowledge of the absolute truth, one cannot describe the activities of the personality of Godhead. Therefore although there are many so-called Ramayanas, or histories of Lord Ramacandra's activities, some of them are not actually authoritative. Sometimes Lord Ramacandra's activities are described in terms of one's own imaginations, speculations or material sentiments. But the characteristics of Lord Ramacandra should not be handled as something imaginary. While describing the history of Lord Ramacandra, Sukadeva Gosvami told Maharaja Pariksit, "You have already heard about the activities of Lord Ramacandra." Apparently, therefore, five thousand years ago there were many Ramayanas, or histories of Lord Ramacandra's activities, and there are many still. But we must select only those books written by tattva-darsis (jnaninas tattva-darsinah), not the books of so-called scholars who claim knowledge only on the basis of a doctorate. This is a warning by Sukadeva Gosvami. Rsibhis tattva-darsibhih. Although the Ramayana composed by Valmiki is a huge literature, the same activities are summarized here by Sukadeva Gosvami in a few verses."