If you looks at most of the games in the chart. The Nvidia cards are foing 16xAA whilst the ATI cards are doing 24xAA which is more taxing for the GPU but gives exceptional IQ. And yes Nvidia have been known to drop IQ to gain more performance. They even put a bug inside the game F.E.A.R so that when an ATI card was used it gave horrid performance (they did this because the game was SLI ready). They were found out by ATI and ATI had to counter act the bug within their own drivers to get the game to work and now the game runs amazingly well on ATI cards.