In the game's DirectX 9.0 mode, AMD's ATI Radeon HD 2900 XT performs exceptionally well, as it consistently outperforms the GeForce 8800 GTX and is faster than the GeForce 8800 Ultra at 1680x1050 and 1600x1200. Having said that, in a blind taste test, you are not going to notice the difference between these cards, as the differences in frame rates are very small. Things change quite dramatically under DirectX 10 though, as the Radeon HD 2900 XT is now the slowest card tested as it suffers a fairly hefty performance drop, while Nvidia's cards saw a slight performance increase across the board. At 1680x1050 and 1600x1200, the Radeon HD 2900 XT delivers a very similar gaming experience to the GeForce 8800 GTS 320MB and 640MB cards, albeit with considerably lower average frame rates – critically though, the minimum frame rate remains close enough to 30fps for the experience to be smooth.

http://www.bit-tech.net/gaming/2007/..._performance/1