More memory space equal faster loads times = FALSE!!!
256 is always faster then 128 = FALSE!!!
If you are using a computer primarily for gaming everyday applications then you aren't going to see an advantage using 256 over a 128 meg card. Their performance is almost identical.
Where 256 megs of memory is most effective is using programs like Adobe Photoshop and Illustrator, also when using multi-monitors.
In the gaming world there is no advantage of using 256 over 128. And if you don't believe me take a look at Tomshardware.com for the data and the testing.