I use an nVidia 6800 Ultra. I picked nVidia for the SLi technology, though if you're not planning on spending about a grand to run dual cards, then that's not a factor you should look at. In reality, there's no real big difference. ATi has some nice hardware accelarating tweaks, but those are more for fun (render any game like the matrix, etc.) Personally, I'd go with another nVidia, I've had little to no trouble with it and it runs great.