There are myriad factors that play into a decision such as this. For me they are as follows:
1) Heat generation: ATI
2) Power consumption: ATI
3) Framerate: ATI
4) Featureset: ATI
5) Price: Tossup
The reason why I gave #3 to ATI is because I trust ATI's framerate right now to be what the benches say they are. Given Nvidia's track record in the driver shenanigans department, I can't say I completely trust the numbers that are being reported by them atm.
I think it's going to take a few weeks when people are able to get their hands on a card before we know for sure. But right now I'll give the benefit of the doubt to ATI in that regard.
I was tempted to give Nvidia the featureset "win" because of their support for 3.0 and, apparently, unbroken ps2.0 support. But 3Dc is just
in terms of "wow" factor. 3.0 just doesn't appear to have that much of an improvement over 2.0 to warrant my caring about it at this point in time.
Now for those that might ask "Well what did you think when ps2.0 came out?" What wowed me more about the 9x00 architecture was its blinding speed and unmatched IQ at the time, not PS 2.0 support. However, I became interested in that when everyone thought HL2 was due last september. Unfortunately no 3.0 titles are on the horizon that push the IQ envelope much past 2.0, according to the screens we've seen thus far.
I just wish Nvidia would cease all activity which gave even the appearance of driver malfeasance. Lord knows we don't need 100 different threads in 2004 on nvidia's driver shenanigans clogging up this forum again. Unfortunately it'll be a long time before I trust an Nvidia solution in my system. Stability is key for me, with IQ coming second, and performance coming third. 3dfx held that title for me from the Voodoo 1 - Voodoo 2. Then Nvidia took it from the TNT2U to the GF2. Now ATI has my money. Hopefully I can get an X800XT (still can't get over how friggin fast that thing is) to replace my 9800 Pro. I want 6xAA/16xAF@1600x1200