First preferences go to Nvidia. I have always had Ati graphic cards and had serious problems with them. Take NVIDIA, seriously. Nvidia's new card have much better minimum fps then what ATI has and that's all that really counts.
ATI has never given me problems, so I have to vouch for them. Never had an nVidia card, never needed one. I've had an ATI 4890 in one of my older machines for years now, and it still can keep up with the latest games like Battlefield 3 on ultra. Pretty impressive lifespan if you ask me.