Ok well take a look at one of the top models from both companies. Ati Radeon 9800XT and the Nvidia Geforce FX 5900

Here is the website for the radeon
http://www.ati.com/products/radeon98...o/compare.html

Here is the website for the Nvidia
http://www.nvidia.com/page/fx_5900.html

Just so you have some info

Personally id use the radeon