Well, the Voodoo5 seems to outperform the GeForce2 MX in higher resolutions (1024x768 and up). If low-res gaming (800x600 and under) is your thing then go with the GeForce2 MX.
But, the GeForce2 MX has hardware T@L, so that's a bonus. It's better for 1-st person shooters.
But, the Voodoo5 has the best FSAA in the business! If you like playing racing sims or flight simulators than the FSAA will really benefit you.