beint af wikipedia:

Advent Children Complete contains a considerable amount of new footage over the original version, as well as roughly a thousand revised scenes. Themes expanded in Advent Children Complete include Cloud's development, Denzel's background, and a more in-depth view of the Turks and Rufus Shinra. As various titles from Compilation of Final Fantasy VII were released after the original film's release, the staff wanted to add links to other titles in the metaseries. There is more violence in this version in to make battles more realistic, most notably the battle between Cloud and Sephiroth, which was also expanded in length. The staff wanted to bring a “dirtier” look to the film, with characters' faces and clothes getting darker and dirtier throughout the battles.