There might be little difference performance wise between V3 and V5. However, there is one difference that I think makes Voodoo 5 more desirable.
You may well know, that Voodoo 3 supports only 16bit colors with 3D, while Voodoo 4 and 5 can use 32bit color screenmodes with 3D. With Voodoo3 you can't run for example Quake2 in window in 32bit Workbench. So you have to use "only" 16bit desktop if you wan't to watch demos/play games (3D). This limitation makes also impossible to use your tv-card in a window with a game/demo on window too, 16bit is just now enough.
