The KJV is the only version that comes from the textus receptus, the manuscript that is an exact copy of the words that christ read and preached during his earthly ministry. It is not to "prefer" the KJV over the others, it is that the others contain errors, which changes doctrine.
Think about the parable in Mt 13:33-35 - the woman who hid the leaven in the three measures of meal. Leaven according to the Lord is false doctrine, Mt. 16:12.
The copies of copies that God has preserved for us today is the manuscript that thousands of martyrs have given their lives for over the past several centuries. The versions of today [with the exception of the KJV 1611] come from the latin vulgate of Jerome, which comes from Alexandria, Egypt, and was rejected by the church fathers as corrupt, but reintroduced by Wescott and Hort when the RSV was put on the market in the 1800's. Using the same corrupt manuscript comes the ASV, NASV, NIV, and all the others we have on todays market place.
The KJV comes from the textus receptus, which means the received text. The one from Alexandria was rejected. The KJV comes from a lot of bloodshed of marytrs who wanted a common text that could be read in language of the people. It was a conviction of many Godly men who risked their lives to give the people this book. Finally the cry to get permission from King James to work on the Bible for the people, brought about the Authorized Version.
Remember the admonition of Rev 22:19, and compare this with Proverbs 30:5,6 about changing just one word Remember it was only one word that was changed in the garden that brought forth the downfall of mankind. Satan cast doubt on the trustworthyness even back then and the same trick is still working now. God said " thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die, ( Gen 2:16,17 ) now compare Gen 3: 4 and the serpent said unto the woman, Ye shall not surely die: see how only one word was changed by the enemy and brought forth the downfall of mankind. there are so many more but no time here. There is a difference when the devil quotes God's Word for his ownpurposes. See the spiritual warfare between the Lord, and our enemy in Mt 4: 1-11, and the Lord always countered "it is written". Especially notice how the devil mistranlates Mt 4:6 from Ps. 91:11, notice how "to keep thee in all thy ways" is left out lest at any time is added, how does your NIV compare?
The new KJV is not the true word of God either. Go to 1 Tim 6:20 and see how the translation committee changed the word **science to knowledge. Why would they do this? Because someone wanted to impress acadamia, instead of standing up for the truth. They could gain acceptance of the educational system, which is really of this world, and a means to an income, not faith in the living God.
By the way, if we are born again of incorrupt seed ( 1 Pet 1:23 ) and I do believe the 1611 is incorrupt seed, of which seed is the NIV? Remember the admonition of Mt. 7:21-23, remember the parable of the tares and the wheat... they both look alike until the harvest.