The central, most important issue in Bible versions is the Greek text of the New Testament (remember, the Hebrew Masoretic Text really isn't under debate). In the King James Bible, the Received Text, which was received from refugees after the fall of Byzantium, became the basis of the English translation. The modern Bibles are all (except for the NKJV) based on the modern Critical Text, which introduces textual changes based on Alexandrian texts and papyrus manuscripts. I've looked at this issue in great detail, and it's mind-numbing. Both sides have written and spoken more words than any sane human being could digest in a lifetime. The amount of material is incredible. Both sides make an airtight case. Who is right? I am honestly not sure.
The key is that the Byzantine text is not as ancient as the Western texts. Greek-speaking Byzantine scribes made a lot of copies of the Bible, and some changes were naturally going to be introduced over the centuries. The Western Roman empire fell much earlier, and the texts from it are older, but were not passed down from generation to generation. What we have is a situation where the oldest texts were preserved naturally, not by being passed down from generation to generation.
At the very bottom of the KJV Only position, which supports the Byzantine manuscripts over the Western ones, is a logical difficulty in the chain of argument. Because they start from their desire to retain the KJV, they build an argument to support the use of both the KJV and the Received Text. Their argument never ends. The KJV language is outmoded and difficult for modern speakers to understand easily, so its use is in decline. Originally, liberal translations like the RSV were sitting ducks for KJV Only attacks, becauseof the badly liberal translations of passages like Isa 7:14 - "young woman" instead of "virgin" which assaulted Christian doctrine. When these Bibles were replaced by conservative modern translations like the NIV, NASB, etc. the original reasons for opposing modern translations changed. To arrest this decline in KJV use, the textual basis of the translations became under attack. (When a translation like the NKJV comes out, based on the Byzantine text, the KJV Only group continues the argument in a new direction, quibbling over translations and footnotes. The bottom line is that absolutely nothing is ever going to be an acceptable replacement for the KJV by definition, and reasons will be found to support this as needed.)
The logical difficulty I have is that the line of argument used to support the Byzantine text could be used, sometimes in a mirror image, to support the Western text. Historically, the Byzantine text was the basis of the KJV. What if the Western text had been the basis of the KJV? The KJV-Only advocates would say the modern text, based on Byzantine manuscripts, added material to the Bible (again, a violation of the prohibition of Revelation). Instead of removing doctrines, they would say the modern text added doctrines not found anywhere else (such as the snake handling in the questionable end of Mark). They would still say was the 500 year tradition of the Western text just a mistake, and the new Byzantine text should be adopted even though it was not historically used? I don't know of any arguments that could be made on one side that couldn't be made on the other. Villification of Westcott and Hort would proceed as usual, only saying they cavalierly added text to the Bible. The same arguments about where will it stop - if someone digs up another manuscript, will that text also be added? - could be used.
This is called begging the question in logic - which means proving your own assumptions. There is absolutely no way, regardless of which text came first, Byzantine or Western, that the KJV Only position would ever be refuted. It's totally airtight, and would be regardless of the situation. This is not a question of whether they are right or wrong. The KJV Only position could be right. The question is that the arguments they advance could never be proved wrong, no matter what the situation was. They would make the exact same case, with the same force, and the same results, even if the Western text had been used for the KJV. They would use the same line of reasoning: the text inherited by the King James translators is correct. The modern text is wrong. Many of the reasons would be mirror images (adding instead of deleting) but the same volume of arguments would be mustered. The deletion of parallel passages which appear in one place in modern translations but not in others is doctrinal corruption, even though the text has the docrtine in one place even if it doesn't have it in another. The "missing" verses are duplicates (Comfort's book discusses this in great detail). Because deleting a duplicate corrupts doctrine, wouldn't adding back a duplicate be the same difference?
The King James Only position could be right. Their line of argument, though, is right in either case. To prove the Byzantine text is correct, they need some line of argument that could be falsified. I haven't encountered that yet.
This does not, obviously, mean that the modern Critical Text is right, either. It could very well be wrong. But the process of reasoning used by textual criticism is more sound. (You can argue, as the KJV Only people do, that the rules of textual criticism are set up to favor one textual tradition over the other. However, there is a long track record of using textual criticism to recover the best text possible of works other than the Bible. It has been used extensively in the classics. If it is not acceptable, no one has ever come up with a better idea.)
Does this settle anything? No, but it cuts down on a lot of the material I have to wade through. When I start hearing the same line of KJV textual argument, I can move on to something else.
Does this mean I don't have faith, because I want this to make sense in human reasoning? I don't think so. I've looked at a lot - maybe all - human religious systems, and the key to them is that you have to throw your reasoning out and accept the nonsense (especially in Eastern religions like Zen and Hinduism) you're taught. It's difficult to keep a straight face when Zen teachers go on with their nonsense. Christianity is the one religion which makes logical sense. You can "come let us reason together" with it. There are some mysteries, like the Trinity, but the systematic unfolding of the plan of salvation through Jesus Christ makes logical sense, both in its own unfolding, and how it fits into the landscape of human history. That's one reason why I am a Calvinist - the Reformed systematic doctrines fit the Bible and the world better than any other version of Christianity.
There may never be a solution. The only solution I have found so far is to have a King James Bible in one hand, and a modern translation in the other, and compare them as I go.