Personally, I can tell the difference between 2x FSAA on a V5 and a GeForce2. If you run 1024x768 and 2x FSAA at 32 bit color in everything, like I do, then the V5 is the ticket. It will do it better and faster than the GeForce if you are looking at FSAA. I'll never play without FSAA again now that I've seen it.
qts is right though, you really have to try playing AH on both of these to see the difference. The nVidia method of FSAA just doesn't work as well as the Voodoo method, especially with a moving picture. If you look around on the web you can find articles that will show you comparative screenshot, but they really only tell half the story. The thing the Voodoo does really well IMHO is remove the flashing and crawling you get from movement. Static screenshots can't show you this.
As for the Radeon, it's FSAA implementation is quite good, and overall visual quality I would rate pretty close to the Voodoo. I don't think it's as fast at FSAA, but I don't really know. I don't trust ATI's drivers, they generally suck, so I won't personally consider them. I do know a couple of guys that have one though, and they are happy with it.
BTW, I checked on the web a bit. You can get a V5 5500 as low as $230 US if you look on
www.pricewatch.com. I couldn't find a price on the radeon though...
------------------
Lephturn - Chief Trainer
A member of The Flying Pigs
http://www.flyingpigs.com 
"My P-47 is a pretty good ship, she took a round coming 'cross the Channel last trip.
Just thinking 'bout my baby and lettin' her rip, always got me through so far."
- Steve Earl