The 9600 Pro has a 400MHz VPU clock and 300MHz RAM clock. The 9600 has a 300MHz VPU and 200MHz RAM clock. So right off the bat, the 9600 Pro is 30% faster than the 9600.
But the 9600 Pro can be overclocked, while the 9600 can't. I've tried all the hacks and nothing worked for me on a 9600, it can't be overclocked in most situations. So that means not only is the 9600 slow, but you simply can't squeeze more out of it.
The amount of video RAM has NEVER been important. 4 years ago you could get a GeForce2 GTS with 32MB or 64MB, and the 32MB version was fine up until 2 years ago. That's 2 years you could have used the cheaper card and not known the difference.
Dealers are scam artist, they have to be in order to compete with the rest of the scam artist. They'll hapily sell you a 256MB GeForce4 MX rather than a 128MB 9800 Pro, and tell you it's better because it has more RAM. They'll be laughing all the way to the bank. But wait! Most dealers don't even CARE about this stuff enough to read reviews and stuff. So they might be lying because they don't know any better. Plausable deniability.
In 3 years, a 256MB 9600 might seem as fast as a 128MB 9600 Pro because newer programs might actually use the extra RAM, but right now you're looking at a HUGE performance drop using the plain 9600.
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