Hmm, So, This answer can be a bit controversial but so is the question. As there is already an argument given from Vaishnava point of view. I am giving point of view from Shaiva-Shakta point of view. To prove my point.
Anyways, Devi bhagwatam is more authentic MahaPurana than krishna bhagwatam (an Upa-Purana) though I can't say if krishna bhagwatam is fake or not but it is definitely not the work of Veda vyasa. Because according to Mahabharata all the 18 Puranas are made before the creation of mahabharata. Krishna bhagvat Purana which is said to have written after Mahabharata will become puran number 19th which is impossible as there are only 18 authentic Puranas. Again, it contradicts with the verses of mahabharata itself which as an author vyasa could not have done. Again as an author someone cannot write 2 books with same name that's insane and also the fact suka died even before the birth of Bhishma himself so reciting krishna bhagwatam was just impossible for him and even according to Mahabharata, king parikshit locked himself inside a specially made palace to save himself from takshaka so he didn't even met anyone at that time. This also contradicts the avatars of Lord Vishnu, where Sri Krishna is said to be the source of Lord Narayana as according to Mahabharata, Lord Narayana is the source of all the avatars including Sri Krishna also.. Plus Veda Vyasa has already mentioned the past times and leelas of Lord Krishna separately in a whole parva (Harivansha) in an itihasa (Mahabharata). Why would he repeat the same thing of same kalpa but differently cz its a real event not some fictional story for god sake. It is said that srimad bhagwatam suppose to have 18000 verses but krishna bhagwatam only has around 14000 rest 4000 are missing where as devi bhagwatam has 18000 verses and it doesn't contradicts mahabharata and also describes the death of suka before the birth of Bheeshma. Even in every Purana devi bhagwatam is described as the 5th Purana to be made so it only means one thing that krishna bhagwatam is a upa Purana written by some one totally different person. Period. Certain scholars attribute this 'Bhagavatpurana' to Vopadeva who is also the author of Mugdhabodha Vyakaranam.
According to skanda Purana.:
“aṣṭādaśapurāṇānāṃ madhye sarvottamaṃ paraṃ ।
devībhāgavataṃ nāma dharmakāmārthamokṣadaṃ ॥” (Skanda Purana : Devi Bhagawata Mahatmayam : Ch1: verse 23)
“Among the list of eighteen Puranas there exists a supreme Purana, the greatest one by the name of ‘Devi Bhagavatam’ which confers all the four pursuits viz. dharma, artha, kama, moksha”.
See the serialisation of the Puranas in Shiva, Vishnu, and Skanda, etc Maha Puranas.:
According to Shiva Maha Purana.:
“brāhmaṃ pādmaṃ vaiṣṇavaṃ śaivaṃ bhāgavataṃ tathā ।
bhaviṣyaṃ nāradīyaṃ ca mārkaṇḍeyamataḥ paraṃ ॥120
āgneyaṃ brahmavaivartaṃ laiṅgaṃ varāhamevaca ।
vāmanākhyaṃ tataḥ kaurmaṃ matsyaṃ garuḍameva ca ॥121
skāndaṃ tathaiva brahmāṇḍākhyaṃ purāṇaṃ ca kīrtitaṃ ।
yaśasyaṃ puṇyadam nṛṇāṃ śrotṛṇām śānkaraṃ yaśaḥ ॥” (Shiva Purana:V:44:120-122)
“Brahma, Padma, vaishnava, Shaiva, Bhagavata, Bhavishya, Narada, Markandeya, Agneya, Brahmavaivarta, Linga, Varaha, Vamana, Kurma, Matsya, Garuda, Skanda, and Brahmanda. These were the eighteen Puranas, which bestow glory and merit to the devotees of Shiva”.
According to vishnu Purana .:
“asṭādaśa purāṇāni purāṇajñāḥ pracakṣate ।
brāhma pāhma vaiṣṇavañca śaivaṃ bhāgavataṃ tathā ।।” (Vishnu Purana 3:06:20)
“Those who are acquainted with the Puráńas enumerate eighteen, or the Bráhma, Pádma, Vaishńava, Śaiva, Bhágavata, and…”.
According to skanda Purana.:
brāhmaṃ purāṇaṃ prathamaṃ dvitīyaṃ pādmamucyate ।
tṛtīyaṃ vaiṣṇavaṃ proktaṃ caturthaṃ śaivamucyate ॥ 7
tato bhāgavato proktaṃ bhaviṣyākhyaṃ tataḥ paraṃ ।” (Skanda Purana: Suta Samhita 01:7-8a)
“First is the Brahma Purana, second comes the Padma, third is the Vishnu, fourth is Shiva, after that comes Bhagavatam (fifth) thereafter comes Bhavishyat Purana”.
According to brahmanda Purana.:
“pañcamī pañcabhūteśī pañcasaṃkhyopacāriṇī ||” (Brahmanda Purana: Lalita Sahasranama: verse 226),
“She is the fifth, the lordess of the five elements, and worshiped with methods comprising five”.
So all these Puranas says that bhagwatam is the 5th Purana that was made, not the last one.
According to srimad Devi byagwatam mahapurana.:
“vāruṇaṃ kālikākhyaṃ ca sāmbaṃ nandikṛtaṃ śubham ।
sauraṃ pārāśaraproktamādityaṃ cātivistaram ॥ 15
māheśvaraṃ bhāgavataṃ vāsiṣṭhaṃ ca savistaram ।
etānyupapurāṇāni kathitāni mahātmabhiḥ ॥” (Devi Bhagawatam 1:03:15-16)
“Varuna Purâna. Kalika Purâna, Samva Purâna, Nandi Kes’wara Purâna, Saura Purâna, Purâna spoken by Parâs’ara, Âditya Purâna, Mahesvara Purâna, Bhâgavatam and Vasistha Purâna. These Upa Purânas are described by the Mahatmas.”
Here you can see there is another bhagvatam Purana is there which is actually an upa Purana described by other Mahatma but not by vedavyasa.
So it concludes that this upa Purana is krishna bhagwatam which is composed by some other author not by Vedavyasa himself.
I know some people will say that krishna bhagwatam is mentioned in other Puranas also. I don't think Veda vyasa himself will go and rewrite his Puranas after completing his “last Purana"(according to other people). The most interesting example is the verses in skanda Puranas which is glorifying krishna bhagwatam as a mahapurana in vishnu khanda thus contradicting itself only as in above verses it has said the same thing about devi bhagwatam. So it's a clear case of interpolation. I haven't seen Ramanujam the originator of Vaishnavas have ever talked about krishna bhagwatam which made Srimad Krishna Bhagwatam clearly as an upa Purana. Where as Seimad Devi Bhagwatam is the real MahaPurana of VedaVyasa.
As for the division of puranas into 3 gunas viz sat, raj and tam thats also illogical as it contradicts Mahabharata and Padma Purana saying that all puranas are the body parts of Sri Hari and gives salvation (thus contradicting itself only which clearly shows the signs of interpolations there).
Padma Purana itself refutes the verse in Swarga Khanda chapter 62 about the classification of the puranas into the gunas viz., sat, raj and tam. (ie. 2.62)
PURANAS--THE EMBODIMENT OF SRIHARI
Puranas are nothing but the mediums through which Sri Hari manifests himself. Brahma Purana is said to be the Forehead of Srihari, Padma Purana is said to be the 'heart' of Srihari, Vishnu Purana is said to be the 'right arm' of Srihari, Shiva Purana is said to be the 'left arm' of Srihari, Shrimad Bhagawat is said to be His 'thigh', Narad Purana is said to be His 'navel', Markendeya Purana is said to be His 'right-foot', Agni Purana is said to be His 'left foot', Bhavishya Purana is said to be His 'right-knee', Brahma Vaivrata Purana is said to be His & apos;left-knee', Linga Purana is said to be His 'right ankle', Varaha Purana is said to be His 'left
ankle', Skanda Purana is said to be the hair on the body of 'Sri Hari, Vamana Purana is said to be His Skin, Kurma Purana is said to be His Back, Matsya Purana is said to be His Stomach, Garuda Purana is said to be His Bone Marrow and Brahmanda Purana is said to be His Bone.
All the Puranas being manifestation of different parts of Sri
Hari's body are very sacred and capable of bestowing salvation.
Here it clearly mentions that " all the Puranas being manifestation of different parts of Sri Hari's body are very sacred and capable of bestowing salvation.
“uvāca sa mahātejā brahmāṇaṃ parameṣṭhinam॥ 67
kṛtaṃ mayedaṃ bhagavankāvyaṃ paramapūjitam।
brahmanvedarahasyaṃ ca yaccāpyabhihitaṃ mayā॥ 68
kṛtaṃ mayedaṃ bhagavankāvyaṃ paramapūjitam। brahmanvedarahasyaṃ ca yaccāpyabhihitaṃ mayā॥ 68sāṅgopaniṣadāṃ caiva vedānāṃ vistarakriyā। itihāsapurāṇānāmunmeṣaṃ nirmitaṃ ca yat॥ 69
bh bhūtaṃ bhavyaṃ bhaviṣyaṃ ca trividhaṃ kālasaṃjñitam। jarāmṛtyubhayavyādhibhāvābhāvaviniścayaḥ॥ 70
vividhasya ca dharmasya hy vividhasya ca dharmasya hyāśramāṇāṃ ca lakṣaṇam। cāturvarṇyavidhānaṃ ca purāṇānāṃ ca kṛtsnaśaḥ॥ 71″ (MBH 1:01:67-71)
“Then the greatly glorious Vyasa, addressing Brahma Parameshthi, said, “O divine Brahma, by me a poem hath been composed which is greatly respected. The mystery of the Veda, and what other subjects have been explained by me; the various rituals of the Upanishads with the Angas; the compilation of the Puranas and history formed by me and named after the three divisions of time, past, present, and future; the determination of the nature of decay, fear, disease, existence, and non-existence, a description of creeds and of the various modes of life; rule for the four castes, and the import of all the Puranas”.
So, Mahabharata itself is Summary of all Purāna.
All Purāna are dependent on Mahabharata as said by Ved-Vyasa.
“asyākhyānasya viṣaye purāṇaṃ vartate dvijāḥ | antarikṣasya viṣaye prajā iva caturvidhāḥ ||” (MBH 1:02:380)
“O ye Brahmana, as the four kinds of creatures (viviparous, oviparous, born of hot moisture and vegetables) are dependent on space for their existence, so the Puranas depend upon this history(Mahabharata)”.
Thus all Purāna are dependent on Mahabharata.
“aṣṭādaśapurāṇānāṃ śravaṇād yat phalaṃ bhavet | tat phalaṃ samavāpnoti viṣṇoḥ nātra saṃśayaḥ ||” (MBH 18:06:97)
“One devoted to Vishnu acquires (through reading this Mahabharata) that merit which is acquired by listening to the eighteen Puranas. There is no doubt in this”.
Here all 18 Maha- Purāna are given equally importance.
So, Mahabharata (VedaVyasa) says that all the Mahabharata is the summary of all the 18 Puranas and all the 18 Puranas depends on Mahabharata itself. So, its every 18 Puranas were written before Mahabharata only and its not possible for a Purana to contradict Mahabharata in the same Kalpa.
Let me give some more proofs to support my claims about Bhagwata Purana.
Chapter 53 of Matsya Purana mentions Kalpas of all Puranas except Brahma and Markandeya Puranas.
Padma Purana - Padma Kalpa (hence the name)
Vishnu Purana - Varaha Kalpa (current Kalpa)
Vayu Purana (includes Shiva Purana) - Sveta Kalpa
Bhagavata Purana - Sarsvata Kalpa
Naradiya Purana - Brhat Kalpa
Agni Purana - Isana Kalpa
Bhavishya Purana - Aghora Kalpa
Brahma Vaivarata Purana - Rathantara Kalpa
Linga Purana - Agneya Kalpa
Varaha Purana - Manava Kalpa
Skanda Purana - Satpurusha Kalpa
Vamana Purana - Kurma Kalpa
Kurma Purana - Lakshmi Kalpa
Matsya Purana - Vaivastara Manvantara of Varaha Kalpa
Brahmanda Purana - Future Kalpas (No specific name
So, here only ,one bhagwatam purana is mentioned which was from sarsvata kalpa.
The Srimad Krishna Bhagavatam states it was written in the present Kalpa:
“parimāṇaṁ ca kālasya kalpa-lakṣaṇa-vigraham | yathā purastād vyākhyāsye pādmaṃ kalpamatho śṛṇu ||” (SB 2:10:47)
Translation: O King, I shall in due course explain the measurement of time in its gross and subtle features with the specific symptoms of each, but for the present let me explain unto you the Pādma-kalpa (i.e. the Svetavaraha Kalpa).
Here you can notice two things 1st it is written in Padma kalpa and it is even saying that Baraha kalpa and Padma kalpa are both same.
As per Chapter 46 of Markandeya Purana,
42. For a hundred of his (Brahma's) years is denominated a Para; and a Parardha or half a Para is well-known to be composed of fifty years.
43. So then a Parardha of his life has elapsed, O brahman; at the close of which occurred the Maha-kalpa, which is famed as the Padma.
44.Of the second Parardha which is now passing, O brahman, the first kalpa (or cycle) ordained is this one called the Varaha.
Lord Brahma's life-span is mentioned hundred (100) years (in which day is known as Kalpa). Lord Brahma's 100 years are known as Para which is his life span.
And Parardha or half a Para is of fifty (50) such years. In another words, Lord Brahma's life-span is of 2 Parardhas.
And at the end of Padma Kalpa (previous Kalpa), first Parardha got over i.e. half life span of Lord Brahma got completed and Lord Brahma is in his second half of life which is Baraha Kalpa.
So from all these above verse we have concluded that theoriginal Bhagwatam of devi was created in sarsvata kalpa where as the upa bhagwatam puran of krishna was created in varaha kalpa or Padma kalpa (as according to them both are same) but we also saw that Padma purana was created in Padma kalpa and vishnu puran was created in baraha kalpa by vyasa.
Again we saw that Baraha and Padma are not the same kalpa both according to markandeya Purana and matsya purana so it is contradicting every other Puranas of vyasa. How is that even possible. Its only possible because it was written by someone else some one totally different person. It's now crystal clear which one is original and which one is a substitute. Period.
Before ending the answer here i want to add one more beautiful thing, which is that VedaVyasa ended every chapter of Srimad Devi Bhagwatam with the following lines.:
Thus, here ends the ___ Chapter of the ___ Book _ On the_(Chapter's Name)_ in the Mahā Purāṇam Śrī Mad Devī Bhāgavatam of 18,000 verses by Maharṣi Veda Vyāsa.
In which VedaVyasa himself proved that its the MahaParana written by him only.
So, I rest my case here.
I hope this clarifies your queries.