There are a few places where translations vary amongst themselves because they give more weight to certain Greek manuscripts of the text over the others.   Although this is somewhat of an oversimplification, there are essentially two “families” of Greek manuscripts that are used in translation.

The most numerous family of manuscripts we frequently call the Textus Receptus.   The so-called "Textus Receptus" is known on a more technical side as the "Byzantine" family, or "Koine".  Many scholars say that it originated in the late third or fourth century near Antioch, and became predominant around Constantinople (hence "Byzantine".)  The most predominant manuscript in this family is the "Codex Alexandrinus" which is the largest contributing manuscript to the King James Version.      

The second family of text is the "Alexandrian" (not to be confused with "Codex Alexadrinus") family of text, which are believed to pre-date the Byzantine family of manuscripts.  The primary manuscripts behind this family are the Codex Vaticanus and Codex Sinaiticus, both which were brought to the scholastic world by a man named Tischendorf  in the last 150 years.   Many scholars believe these to be the most reliable family of manuscripts, although that is a very debatable topic.

 In a nutshell, the King James, New King James, and King James II give precedence to the Byzantine family of texts – which some people will refer to as the “majority” text. 

Most other translations give precedence to the Alexandrian family of texts, also referred to as the “critical texts”.      

No crucial doctrinal issue rises or falls on the differences in any of the manuscripts.  For a more detailed discussion of the differenced in the two manuscript families, and how it relates to what is known as the “King James Only” Controversy, you can follow this link HERE. http://www.earlychurch.net/KJVO.htm