If our desire is to have an accurate and understandable representation of the original texts of the Bible, the King James Version is not a good choice.
Nor is the NKJV. Though the NKJV provides a modern English rewording of the KJV wording, the NKJV still has all of the same errors that the KJV derived from Erasmus' Greek New Testament, which is plagued with corrupt readings.
Truly major differences between the KJV and modern translations of the New Testament are primarily due to the inaccuracy of the so-called Textus Receptus [TR], the Greek text upon which the KJV's New Testament was based. According to Bruce Metzger (The Text of the New Testament: Its Transmission, Corruption, and Restoration, Third Edition, Oxford University Press, 1992, pages 95-118), the TR primarily resulted from the work of a Dutch Roman Catholic priest and Greek scholar by the name of Desiderius Erasmus, who published his first Greek New Testament text in 1516. The first edition of Erasmus' text was hastily and haphazardly prepared over the extremely short period of only five months. That edition was based mostly upon two inferior twelfth century Greek manuscripts, which were the only manuscripts available to Erasmus "on the spur of the moment"
1Jo 5:7,8 - an example of textual corruption. "in heaven, the Father, the Word, and the Holy Ghost; and these three are one. And there are three that bear witness in earth."
Erasmus' final 1535 edition still relied upon no more than six Greek manuscripts, the oldest (but least used!) of which was from the tenth century. Though Erasmus did in later editions of his work consult the Complutensian version of the Greek New Testament, Metzger is able to truthfully state:
Thus the text of Erasmus' Greek New Testament rests upon a half-dozen minuscule manuscripts. The oldest and best of these manuscripts (codex I, a minuscule of the tenth century, which agree agrees often with the earlier uncial text) he used least, because he was afraid of its supposedly erratic text! [Metzger, p. 102]]
Due to the errors in the Hebrew and Greek texts from which the KJV were translated, the KJV contains some texts that are not consistent with Jesus' genuine teachings and other genuine New Testament teachings, as represented in the earliest Greek texts of the New Testament.