Between the Bible and the Book of Mormon, which one has a more plausible alternate account of its invention?

If one is to reject the validity of that account, they would need to be able to present a plausible alternative explanation to explain how and why that work was created.

do they? isnt the onus on the one making those claims?

Is there any consensus on which of the two works would have a more simple alternate explanation?

Using someone like Joseph Smith against the entire swathe of Christianity is a bit unfair, because the creation and development of his religion is well documented, and it was in fairly recent memory. But in both cases, the central claim of communication with God is just one of those "youll have to trust me" kind of things. I mean, unless God's going round telling different things to everyone he speaks to, one of those groups has to be wrong, they have conflicting claims.

Is there any consensus on which of the two works would have a more simple alternate explanation?

Mormons because their history is shorter, but they are both as simple as each other: definitely terrestrial in origin, with claims of divinity in the authorship

Plausible: An argument or statement seeming reasonable, probable, or credible.

The man, Joseph Smith is the single, sole source of the Mormon "revelation." That means that if Joseph Smith had never been born, we would have no knowledge of any portion of the LDS "revelation," its "scripture" and it's supposed "restoration." We would have no reason nor any other source from which to derive any reason to think that any portion of the "Mormon" scriptures (such as the Book of Mormon or the so-called "Book of Abraham," or the D&C would have ever even existed let alone have any reason to believe their contents.

On the other hand, the content of the Bible enjoys the benefit of what Historians call "multiple independent attestation." That is, the events, people and places recorded in the Bible very often are represented in multiple and frequently unrelated sources, (literary, physical artifacts, verified locations, etc).

What this means is the even if the Bible were never written, many of the people, places and events recorded in its pages would still be documented or represented for us in the plethora of diverse types of evidence from history. The simple fact is, many of the people, places and events recorded in the Bible are deeply and inexorably woven into the fabric of history itself and thus, as one might expect, those people, places and events were observed, recorded and represented in many places from many different points of view. I mention this here to provide an example of commonly recognized REALITY that stands in strong, even stark, glaring contrast to the claims of Mormonism.

Therefore, it is reasonable to ask, ...why should we believe him since there is exactly nothing in Mormonism's unique claims that would have ever been even mentioned on earth if Smith had never been born.

Since the Book of Mormon claims to be an historical document it should be examined on that basis to determine its authenticity. If the BoM civilizations really did at least exist, where are the multiple lines of evidence that would necessarily indicate this? It is certainly true that all other large ancient civilizations left an abundance of diverse evidence of themselves. It's even true of MANY tiny little tribes. Why do the claims of Mormonism require or deserve special pleading?

If Joseph Smith was a real prophet of God, then why are there no facts to establish the fulfillment of his many rather grandiose predictions about events that would most certainly have been clearly observable when those predictions came true? Where is there any evidence that the events he predicted (such as the return of Christ in the 1800s, the fall of the U.S. government or the building of "THE" temple in Missouri, etc.) actually came to pass as he said that it would?

Dr. Hugh Nibley was an American scholar and apologist of The Church of Jesus Christ of Latter-day Saints, and was a professor at Brigham Young University for nearly 50 years. Here is what he stated. "The Book of Mormon can and should be tested. It invites criticism."

Brigham Young stated, "Take up the Bible, compare the religion of the Latter-day Saints with it, and see if it will stand the test." "J&D volumn 16, p. 46, 1873.

Orson Pratt: "Convince us of our errors of Doctrine, if we have any by reason, by logical arguments, or by the Word of God and we will ever be grateful for the information and you will even have the pleasing reflections that you have been instruments in the hands of God of redeeming your fellow beings." "The Seer, p. 15.

Which book has a more plausible alternative explanation? I assume that you are asking, in other words, "which book has the least evidence it was written by God?"

Let's take a look at both, and discuss what we find. We will start with the Bible.

The Bible was written over a very long period of time, in different parts, on two different continents, and by different people and authors. It was also collected and preserved by many different people and in many different places and at different times, and in different languages. There are many different translations available, and differences between translations and manuscripts can be publically compared. To go and fabricate all of the Bible, or change all of the manuscripts, would be completely impossible. It would be possible for the Bible to be nothing more than folklore, but even if it were only folklore, we would still have to trust its historical integrity and provenance as a document.

So is the Bible from God? The questioner who asks whether the Bible is God's word communicated through men may choose to disbelieve the message that the Bible teaches, but would also have to account for it being more than just folklore or historical fiction based on the archeological evidence it uniquely presents (Jericho or Sodom are great shorthand examples), the historical evidence it provides (David we now know to be a historical figure, the Hittite people were discovered in archeology thanks to the Bible), and prophetic evidences (like the prophecies that prefigure and predict elements of Jesus' life, for example) that the Bible contains. They would also still have to wrestle with it's theological message.

In contrast, the Book of Mormon, assuming that it existed originally as gold plates (which I think is hard to prove, but we will assume it to be true for the sake of argument) would have been very easy for a small group of people to manipulate, edit, contrive, or even destroy, as it was controlled completely by a very small group of people; and its translation and original distribution happened during a very short period of time and was seemingly under the exclusive control of the Mormon church. The validity and trustworthiness of the book of Mormon as an accurate translation or document hinges entirely upon the trustworthiness of only one man, Joseph Smith, and unfortunately, he cannot be seen as an unbiased or uninterested party, as he was also the one person with the most to gain or lose from its acceptance or rejection.

If then the book of Mormon is assumed to be an accurate translation by Jospeh Smith, and it is only taken at face value (that is, without examining its provenance but only its message), it cannot be said to contain any historically verifiable events (there are no other ancient historians or documents or relics that reference the people groups or individuals mentioned in the BOM, as there are in the case of Josephus or ruins that mention King David by name for the Bible), nor any archeological evidence that confirms or supports the claims in the BOM (BOM talks about animals and plants in the New World that have never been found here before the Europeans arrive). There may be some prophetic utterances in the BOM that seem to provide evidence for its divinity, but prophecy is very hard to use as definitive 'proof' because of its need for correct interpretation, and therefore isn't a good primary argument for its divine authorship (this applies to the Bible as well).

All in all, there are many people that believe in both books, and people that reject both books, but there is no one who believes exclusively in the book of Mormon while rejecting the Bible as God's word - the opposite is true, however, there are many people who reject the BOM, but believe exclusively in the Bible as God's word.

Given the evidence and arguments laid out, the Book of Mormon seems less likely to be the word of God than the Bible.