Nvidia hasn’t showed any sign for supporting the 3DFX Cards series. It has been (if i’m correct) over a year now that they bought 3DFX and I haven’t seen one driver update from Nvidia. So buying a Voodoo card these days is gamble.
The Voodoo 4 4500 and the Voodoo 5500 that i use at work everyday are great cards. Haven’t seen any compatibility issues at all. So if you do buy one, it should work nicely.
But if I had to choose, I would go with a GeForce.