Should I go for the video card with more vram (video ram)?
More video ram is indeed better, and if you have the money, go for it. Currently 512MB is the sweet spot, anything more is pointless, unless you use 1600 x 1200 or greater. If you use 1280 x 1024 or smaller, 256MB of video ram should be fine, although it still fills up quickly in newer games. Unless you play on 800 x 600 or lower, I would not recommend 128MB video cards. Sometimes, more video ram just isn’t worth it if the video card isn’t powerful enough to take advantage of it. You will not see the difference between a 7600GS 256MB from a 7600GS 512MB, no matter what resolution.