OK what I've been able to gather so far is that it has:
- different/censored fmv video files
- different menu music and background (why?)
- added save game feature (making it easier)
- changed item layouts
- various rendering issues
oh and of course on modern windows is lacks EAX. AVP is well known as the poster child of EAX that really used it to enhance the game. So this is a major omission.
and I'm guessing these issues aren't the only ones. so highly disappointing that you can't get an authentic game these days. why do devs not care about preserving history? it's george lucas all over again. might as well emulate it in that case.
The lack of EAX support on Windows 10 is not GOG’s fault. EAX (by Creative Labs) hasn’t been supported by Windows since Windows 7/Vista. Besides, EAX was a Creative Labs only thing.
But with a few tricks you can add EAX support to your system again and run it on any soundcard.