oh yeah, if i'm not mistaken, ATI has better single GPU core graphic cards, nVid is pulling ahead thanks to their Dual GPU card, the 7950.

That my friend is the question of the century. Whereas Nvidia is naturally more stable in games especially those ones that use OpenGL, ATI unfortunately has some rather disturbing support issues in relation to their drivers. Ive had both a Nvidia and ATI video card and yet i find when playing games such as Doom 3 the framerate is much more constant even during rather intense scenes, whereas ATi can not always maintain this consistency. Nvidia also has the lead card out on the market with its 8800 series which is worth more than a decent computer in itself, however if you are unwilling to pay gross amounts for a video card with decent performance on of THE best value for money cards out there is ATi's X1950 PRO the equivalent nvidia card being the 7900GT i think. I guess it comes down to what mobo combo you have and whether you play OpenGL games more or less.