I'll go with nvidia too. I've got nothing against ati but I've always used nvidia and I've always been very satisfied with the price/performance ratio. Also nvidia has good drivers for linux.
first off...geforce...already has lower end options and the high end options for a direct x10 card....always ahead of ati...that simple...now radeon cards are still quality cards dont get me wrong..and there new dx10 cards are mighty fast but nvidia seems to be a step ahead...also note that nvidia makes good motherboards..and even great video cards for cellular phones too!