I have had both Nvidia and ATI, their both good cards, just one always trying to out do the others. The first two are excellent choices for Nvidia.
The third one Saphire for ATI is not a good choice right now. I have read numerous complaints on these forums about problems with Saphire. No matter how cheap it may seem stay away, because you will get what you pay for.
BTW: Most here seem to be ATI fans, so they will always choose ATI over NVidia. I have use both and have been very happy.
