The 3D prophet 4500 utilises a tile based rendering architecture which makes it really very fast for it's price. It, however, sports the smallest feature set of any current card (that i'm aware of). The Geforce 3 has the biggest feature set of any current card, even slightly beating out the radeon in that respect.
in terms of speed they may actually be about the same in many situations, the prophet 4500 will probably lead in situations where there is great depth complexity. (you'd be suprised how much overdraw there is in a lot of current games)
But the prophet 4500s low feature set means that it will probably not have too much longevity (not that any current video card will still seem attractive in a year or so), however it may be worth considering for it's low price..
The Geforce3s price is probably going to decrease significanly once the Radeon 2 is released (september, i hear) so you might wanna consider waiting a bit.
