Right as of now nvidia is on top. When the R600 comes out things will start to heat up. ATI has always had slghtly better top range cards while nvidida has better mid range cards. I buy the mid range cards. That is why I choose nvidia.
AMD owns ATI now dont they, so they will be following their marketing strategies, not sure if this is a good thing lol, i want AMD to come out with a Core duo shattering chip.
easy, nvidia of course. Always had a nvidia card (that would be 3 cards) and never had a single problem with any of them, and I've always been satisfied with the price/performance ratio.
Also great drivers for linux, which is always a big +.