Here's my convincing argument for ATI. I had a very similar card in my previous machine. A GeForce 2 GTS which served me very faithfully for over 3 years now. A slightly less powerful version of your GeForce 2 Pro.
Anyways, after all the reading, all the arguments, all of the technical support and problems and whatnot. I am now a convert to the ATI side of things. The latest FX models were both expensive and disappointing and although performance has been ramped up recently, the "Flow FX" fan/lawnmower is far too noisy, and takes up an extra PCI slot better left to something else. The Radeon 9700 in my machine performs at breackneck speeds...it has top notch image quality and so far my only complaints with anything video is that the really high resolutions in some games that I can achieve with constant FPS makes the text too small to read

The FX 5900 does improve apon these things and right now its neck and neck with the Radeon 9800 256mb. However, if you aren't going to buy the TOP OF THE LINE model such as those two cards then the ATI middle of the road is far better than the nVidia middle of the road in terms of new cards right now.
A bargin deal is a GeForce 4 TI 4200. Good card, but no DX9. You won't get a similarly powerful ATI model at that price. But in this sort of mid range where the FX 5200, 5600, 5800 and the Radeons 9500, 9600, 9700 reign...the Radeons are the better choice.
Or wait till next year when the FX 5900 is a bargin chip and nVidia has something new
