I'm sure he probably meant that the game is more optimized for NVidia cards since they apparently supplied him with some samples. Then again he's not likely to ignore over 1/2 the market and not do some optimizing for ATI cards as well. A lot of games that were optimized for one usually only run a few FPS better than the competitor.

As far as looking different on one card compared to the other . . . I don't think you can really do that.