The NASB and NIV, two very common translations used by Protestants are both based on scholarly reconstructions of the texts of the New Testament done by Nestle-Aland and the UBS.
The major competing version with NA and UBS is the "Majority Text" used by some translations such as the NKJV. The state of New Testament scholarship is very much in flux, as the various sides debate the merits of various texts and reconstructions.
All of this is of minimal importance unless you require absolutely perfect copies of the originals, as is necessary if one is to follow Sola Scriptura.