I work as a hardware editor, i review video cards for a swedish website, exactly like Toms Hardware and other international websites does. I currently have the following cards on my desk, as we speak:
Radeon 9800 XT
Radeon 9800 Pro
Radeon 9700 Pro
Radeon 9600 XT
Radeon 9600
Geforce FX 5950 Ultra
Geforce FX 5900
Geforce FX 5900 XT
Geforce FX 5700
Geforce FX 5600
Geforce FX 5200
And a couple of older ones such as Geforce 4 etc.
I have benchmarked and tested all of these cards with the following drivers:
Catalyst 4.1
Catalyst 3.10
Catalyst 3.9
Forceware (Detonator) 53.03
Forceware (Detonator) 52.16
The test rig i use to test video cards has 25 GB of games installed, including Neverwinter Nights.
The problem with NWN everyone speaks of, is minimal, and I wouldn't base my decision on it. Anandtech has some good information on the subject here:
http://www.anandtech.com/video/showdoc.html?i=1896&p=26
NWN was created when everyone used NVidia hardware such as Geforce 3's and Geforce 4's, therefore Black Isle/Bioware implanted some nVidia specific optimizations to improve anti-aliasing (you can clearly see this in the configuration program where you can set the AA slider to Quincunx, which is NVidia only). Now, everything is different. ATi is
larger than ever. Most newer DX 9 games are created by game developers with Radeon cards in their development rigs. This will lead to some problems with NVidia hardware. It has always been like this. Unfortunately, no video card driver is perfect.
That said, I think Radeon is generally a better choice at the moment. Sure, there are exceptions (The Geforce 5900 XT is a great $200 card), but ATi simply offers better performance and less problems (such as driver cheating) when it comes to the newer generation of games. If you only want a graphics card to play older games such as NWN, go for a Geforce 4. If you want something that will work just fine in the future, Radeon is the way to go.