Originally posted by Jonesie
A 256 card will run better than a 128 card because it can process the images faster etc...Some people don't seed the need in a 256 card, but if you plan on doing gaming and want high performace, you should really go with the 256 card.
The differences right now are minimal so it is my consumer opinion that is not worth to fork out for a 256 mb card. Instead just get the 128 mb version. The average fps difference is like 1-3 fps.
Also it depends how much money you got and what type of games you play or what are you going to use the GPU for.
If you're only going to use the GPU for video playback you don't need to spend a ton on it.
Most gamers consider the 9600XT as the absolute minimum you should buy. But 9800 pro is the ATI mainstream card now and I recommend buying that since by next year most gamers will recommend 9800 pro as the minimum.
For Nvidia, many peeople feel the FX series are rubbish because their DX9 support is less than stellar. The 6600 GT is an amazing card and it easily outperforms the 9800 pro so if you're thinking of buying a Nvidia card get that one.
Also when you buy a GPU you have to take your system into consideration. If you're running a P4 1.4 buying anything better than a 9600 would be a waste of money since your PC will bottleneck your card.
Same thing as the other way around. If you have a AMD64 and you buy a 9550 the GPU will bottleneck your graphical experience.
If you buy a 9800 pro anything less than a P4 2.0 and 512 mb ram will bottleneck its performance.
You also gotta take into consideration of your PSU. Watts is usually a measure but one thing I have noticed with PSUs are that if you have a top quality 400W PSU it will be better than a generic 600W PSU.
Also other things to keep in mind...ATI has "levels" for its products. They are (from best to worse):
Don't buy ANY SE versions.
Also if for some reason you're looking at a GeForce 4 don't buy the MX series.