hi friend, i want to ask u... and i need help too,, between Ati Radeon and NVidia... give your choice...
#1 if we want to use that GPU for gaming.. we should see that who's the game company support. for example: Nvidia is company who fully support for CRYSIS game. #2 we have to combined the GPU with the Processor best blend. #3 in my research.. ATI Radeon is best for gaming and Nvidia is best for Multimedia ( in all case ). #4 ATI with 48xx series or higher.. is easier then GTX 27x series.. for overclocking. #5 many Nvidia product more coolest than ATI for overclocking.
I prefer Nvidia , check this list of top 5 graphic cards: http://techjungle.info/top-5-graphic-cards-of-2010/
many website have a different way for rate their hardware. so you can't base to 1 or 2 site. you have to looking for a what case before.. ^^
Really it's personal preference, I wouldn't be bothered too much as recent cards should have the ability to do whatever it is you need to do, since the technologies are comparable. Sure, there may be pros/cons between the two, as with any product.