I think ATI makes a valid point that if the game you like is not a mainstream game that sells a million copies and has benchmark results posted in magazines you will never see this level of optimization from Nivida.
So if all you play is mainstream games your choice is ATI/Nivida, if you play some of those games that are off the beaten path then I guess ATI is the only way to go for overall performance.
Unless someone else has a better explanation.
AMD 64 3000 + - 1 GB Kingston HyperX - Chaintech ZNF-150 MB - Audigy 2 Gamer ZS - 200GB SATA HD -
ATI X800 Pro OC 520/540 - 21" Cybervison monitor - Thermaltake Butterfly 450 watt PS - UFO Custom Case