PDB said:

Even though returns was the first offical dolby digital soundtrack I think the dolby stereo surround is still worth saving/preserving as that would of been the way most people would of heard it in the theater at the time. Dolby digital was new and hadn't reached market penetration yet (although it quickly did). At the end of the day it is probably closer to the original theatrical mix then anything else (although that's a guess).

As I understand it the DS mix from Returns was a fold down from the original 5.1