Hmm, it's been my experience that between the two ATI tends to make slightly superior hardware with somewhat poor driver and software support, while nVidia does a pretty consistent good job with drivers.
I wonder why ATI seems to have fallen so far behind on the latest generation? Seems to be a first for them. All they've managed so far is a paper launch. Probably catch back up with the next generation.
As far as drivers, nVidia has always been very quick about fixes for specific games throughout the 4 cards of theirs I've owned. The two ATI cards, on the other hand... The first one I had was a few years ago, when ATI's drivers were absolutely horrible. For every bug they fixed, they seemed to break something else or unfix something. Then, with the drivers still broken, they dropped support for the card and no longer updated drivers. So, I didn't like ATI too much. Admittedly their drivers have come a
long way from how the used to be.
A while back, when the Radeon 9700 was fairly new, I relented and bought one of those, since I'd seen so many good framerate tests and such. Switched from my older Geforce card, and the Radeon driver installation process came up with an error message and crashed partway through. Tried again, it would crash in the same place. Apparently not an uncommon problem, from checking online. Since the installation had added the driver files, I was able to manually install them without another problem. I forget what game I tried first, but I do remember it had some graphical corruption bug and that the game randomly crashed. The graphic glitch was apprently known by ATI and they eventually fixed it. Turns out the crashing was a bug with the game, but at the time I was quite willing to blame the card. Took the video card back to the store and got another Geforce instead after having those problems. Everything was great then.
I think ATI has further improved their drivers, and their antialising is better in some respects, but they've sufficiently ticked me off so that I'm not buying an ATI card again.
So to sum it up for me, ATI=good hardware, nVidia=stable drivers;nVidia=winner.
[/tired ramble]
BTW, good pick with NewEgg, it rules them all. I wuv NewEgg.