Late to the party, but I remember the original game had some pretty cool music that is not included in this new version. Otherwise this game has done nothing but improve over time!
Late to your lateness but I think the original "Reprisal" pre Universe mainly had the Resistor Anthems by Eric Skiff and the older video trailers also credited him. You might also find older demos of Reprisal on Newgrounds when feeling particularly nostalgic.