Currently the Nvidia 6800 has the best performance although Ati just released better OpenGL drivers which give the X800 a 10% boost in Doom3.
But Doom3 is the only thing 6800 is good at - X800 is better for everything else.
Originally Posted by Dead and Gone
all the ATi cards are having quite bad performance and display problems with Doom 3...
What sort of display problems are you talking about?
With my X800 I can run Doom3 @1600x1200 2xAA 2xAF quite smoothly and without display problems.
ps. X800 Pro VIVOs are actually X800XT PEs. All they have done is disable four pipes and lower the clocks with a bios mod. So if you want a cheap XT PE just buy a Pro VIVO and flash it with the XT PE bios.
Some of the Pros even have XT stickers on the heatsink.