There were two main sources for the Bibles we have today.
One line is the antioch text line and the other is the alexandrian text line.
Today the main difference is between the textus receptus or the works of the heretic anti-Christians westcot and hort.
The Authorized Version, like all the early Protestant Bibles of countries such as Switzerland, Germany, Holland, France, Spain, Italy etc. was translated from a Text called in the early Reformation days the Received Text (Textus Receptus). Before that time this Text, also known as the Majority Text, was used by the early church in Israel, the Middle East, Asia Minor and Greece. In those lands we see the Almighty preserving His inspired Word as He promised to do. Because of its purity the Received Text was then used by all the early Protestant Reformers of Europe for their translations. Textus Receptus also became the basis of the Authorized Version.
The Westcott / Hort / Nestle / Aland Greek Text
But a strange and dangerous development began to occur towards the end of the 19th century. New translations of the Bible, based on a vastly different Greek text, known initially as the Westcott/Hort (W/H) Greek text, began to appear. This text later became the basis of the Nestle/Aland Text which underlies virtually every modern translation of the Bible published since 1881.
According to the Rev. Jack. A. Moorman's book Missing in Modern Bibles - Is the Full Story Being Told? the Nestle/Aland Greek Text is shorter than Textus Receptus by 2886 words! Those 2886 words are equivalent to the books of 1st and 2nd Peter.
The difference between Textus Receptus (TR) and the W/H Nestle/Aland texts is caused by two ancient manuscripts (Codex Sinaiticus (Aleph) and Codex Vaticanus (B)). The TR excludes these two manuscripts. The Nestle/Aland text includes them. Codex Sinaiticus was retrieved from a wastepaper basket in a convent at the foot of Mount Sinai in A.D.1844. Codex Vaticanus, a 4th century document, was found in 1481 in the Vatican library in Rome, where it had lain virtually unused for over a thousand years. These two ancient manuscripts, both of which were considered unfit for use even by their own custodians, were seized upon in the later half of the 19th century and foisted on the unsuspecting Christian church in place of the trusted Textus Receptus. The following reference from page 554 of G.A.Ripplinger's book New Age Versions (ISBN 0-9635845-0-2) refers:
"Metzger says that Sinaiticus and Vaticanus do not agree with the majority of manuscripts.
Not only do they disagree with the Majority of manuscripts , but they do not agree with each other. The 8000 changes in B and the 9000 changes in Aleph are not the same changes. When their changes are added together, they alter the Majority text in about 13,000 places. This is two changes for every verse. Together they omit 4000 words, add 2000, transpose 3500, and modify 2000.
They disagree with each other a dozen times on every page.
Colwell says they disagree 70% of the time and in almost every verse of the gospels. Burgon says: 'It is easier to find two consecutive verses in which these manuscripts differ than two in which they agree."