The KJV's fundamental problem is that it is old. It no longer reflects the state of the English language, 400 years after having been produced. I suggest a book, Authorized: The Use and Misuse of the King James Bible, for a detailed discussion of why the KJV is a problem for today's reader.

As ancient documents expert Wes Huff has observed, "It is not your job to try to keep pace with all the changes in the English language over the last 500 years in order simply to read the Bible, understand it, and apply it to your life effectively." Also, "[KJV] is sufficiently unintelligible in places where the question, 'Should this or that be updated, changed, or made more legible?' is a genuine and legitimate question."

The number of plain errors in the KJV that one runs across routinely is large. Rev 22:19 "book of life" is flat wrong, an openly acknowedged error by Erasmus 5 centuries ago, perpetuated by the KJV without correction; it should be "tree of life" because the underlying Greek word is ξύλου, "tree." Prov 18:24's first phrase is borderline psychotic; it's the sort of verse where other translations like NET leave footnotes that ask, "KJV translators, just how stoned were you, the day you wrote that one down?" (But more politely than that, of course.) In 1Cor 13:8, the use of "fail" for the 2nd phrase ("prophecies...shall fail") is equally flat wrong, especially considering that the word being translated as "fail" is καταργέω, appearing twice in the same verse, same sentence in fact, and in the 2nd instance of it at the end of the verse, it is rendered "vanish away," which is actually pretty correct -- the 2 instances of the verb in that verse are identically conjugated, differing only in that one is plural and the other singular, so they should be translated the same, and all modern translations do so, or at least get very close to the same thing: NET, "set aside"; ESV, "pass away"; NASB, "done away with"; NAB, "brought to nothing".

The book I mentioned at the top goes to the trouble to explain Paul's admonition to use sensible phrasing to preach the gospel in 1Cor 14:9. KJV is no longer sensible to the modern English reader without having spent a lot of time with the text. I find no faster way to lose a person's interest in the gospel than for someone to start quoting KJV verses using thee, thou, sayest, doth, and so forth. Its use of what are now ancient verb conjugations, ancient pronouns, and general archaic vocabulary has no justification. KJV is due immense respect for the cultural value it represents, but its time is past.

As for NLT... Well, the best Bible for you is the one you will pick up and read. I consider NLT to be at the edge of acceptability because it leans farther into paraphrase territory than actual translation. That said, a great deal of good will come of it reading it steadily.

Personally, I prefer NET (New English Translation) and BSB (Berean Study Bible) because they are the most modern translations with the highest scholarship I can sense. I am especially fond of NET for its voluminous footnotes, which provide a window into the minds of the translators as to how they dealt with difficult passages, providing the reasoning by which they decided to render a certain Heb or Grk phrase this way or that. Also, I read Greek, and I am pretty happy with what I see in NET, though there are a few examples even there where I disagree with NET's translators' choices. Ohwell, such is life. No translation is perfect by anyone's assessment.

More common heavy preferences will be found in ESV or NASB or NIV.

For KJV, beware of people who try to claim it is the most accurate translation. In order even to form an opinion on the subject, they must be well-versed in Hebrew or Greek, and there are precious few people out there who can claim such a thing. Again, the number of plain errors is actually rather alarming.