FYI, the stress test is a bunch of shader effects used in half-life. It is not indicative of HL-2 gameplay performance. It's a pure rendering test of a card's ability to render the most advanced effects used in HL2.
http://www.gamers-depot.com/hardware/video_cards/source/001.htm
Basically, in the high end line the ATI-x800XT-PE ($550) is ~10% faster than nvidia-6800-ultra ($500). However, the $400 line on both cards (x800 Pro and 6800GT) are pretty much dead even in performance.
However, there are graphical anomalies with ATI hardware. If you look in the screenshots, there is color/lighting banding where the nvidia-6800 is flawless.
http://www.gamers-depot.com/hardware/video_cards/source/001.htm
Basically, in the high end line the ATI-x800XT-PE ($550) is ~10% faster than nvidia-6800-ultra ($500). However, the $400 line on both cards (x800 Pro and 6800GT) are pretty much dead even in performance.
However, there are graphical anomalies with ATI hardware. If you look in the screenshots, there is color/lighting banding where the nvidia-6800 is flawless.