I made the same move.
You'll need at least Quincux AA on the GeForce 4 to equal the 2x FSAA on the Voodoo 5 IMO. I've had both. The Voodoo's image quality is still better than the GeForce 4. 4x FSAA on the GeForce 4 is what it takes to equal or surpass 2x on the Voodoo 5 IMO.
Sigh. I like my new GeForce 4 Ti4200, but what a shame to have lost 3DFX...