My foundational testimony of the Book of Mormon is not about exact content, so much as how it "speaks to me". ("crying from the dust" - I really like that image.) I really like it and it seems to be the inspired word of God - certainly every bit as much as the Bible. There are lots of passages I really like, content-wise, but that's never been what it's about for me.
Having said that, I really do see some things as almost impossible to "fake" within the text itself.
The dichotomy between the Book of Ether and the rest of it is just one example of this. It is amazingly compelling, if you have studied much of the cultural differences between the Middle East and Northeast Asia - and, if I am right, it basically solves the DNA issue on a theoretical level. Therefore, even without my spiritual testimony, relying only on my intellect, I just can't see it as an intentional fraud.
One really important thing to understand, imo, is that there really isn't any more physical proof of most of the important claims in the Bible (especially the Old Testament) than there are for those in the Book of Mormon. Most people don't realize how shaky the non-religious / non-spiritual "proof" for the Bible is, particularly when it comes to the accuracy of the New Testament teachings and just about everything in the Old Testament. Even most ardent Christian historians agree that the accounts in the New Testament were written after the fact (sometimes long after the fact) and by people other than the purported authors - and were taken from multiple, conflicting source materials; hence, all the hoopla in the early centuries about which writings to include and which to exclude in the formal compilation we know now as the Bible.
For example, from a purely "historical" perspective (taking away all claims of source and method of discovery and translation), the Book of Mormon is MUCH easier to accept as scientifically plausible than the Bible - since there is FAR less of the miraculous chronicled in it than in the Bible (and those things that are presented as miraculous generally are much easier to explain as non-miraculous).
Furthermore, it's interesting to realize that most of the truly unique "doctrines" in Mormonism are not found in the Book of Mormon. In fact, there are almost none in it. Nearly all of them are in the Bible and the D&C - and nearly all of the ones in the D&C are presented as revelations received as a result of contemplating Biblical passages or specific issues of the time.
Finally, the Book of Mormon itself doesn't claim to be something that should be read instead of the Bible - or even contrasted with it. Rather, it says explicitly, more than once, that one of its central purposes is to convince people to believe the Bible. That wording is interesting in its implications, since, in one case, it explicitly says it is intended to help those who "believe in the Bible" actually believe the Bible (what it teaches). Based on what it actually says, it's supposed to be a supporting companion to the Bible, not a superior work. Thus, Joseph's "most correct" words notwithstanding, pitting it against the Bible simply isn't consistent with its stated purpose - and I regularly go back and forth between it and the Bible in my own study.
(I've said more than once that I think Joseph didn't really understand the Book of Mormon very well - at least not what it actually says in its pages. I think he simply didn't care about it as a proof text, so he didn't "study" it to understand doctrine. Ironically, that's one reason I have a hard time accepting it as conscious fiction. Every author I've known understood their works much better than Joseph appears to have understood the Book of Mormon.)
None of the above proves anything regarding the nature of the Book of Mormon, but it's important to keep in mind when comparing it with the Bible - and it's an important part of my own testimony regarding it. We've inherited a lens through which we "naturally" see the Book of Mormon, and that lens, imo, is one of the "incorrect traditions of (our) fathers". As a result, I think relatively few members understand the Book of Mormon really well - at least when focused on what it can teach us as not just as a canon of scripture but also as the spiritual-history-journal abridgment it claims to be.