With World in Conflict, we'll try the same strategy we used with Far Cry 2: we'll run once with the highest settings available, and then once again with 4xAA and 16x anisotropic filtering (AF) in order to increase texture memory usage.
Now for the first run results:
There appear to be no significant differences of which to speak. Now, let's add 4xAA and 16xAF:
It's a very close race. The 512MB card does seem to suffer a minor performance penalty at 2560x1900, but at 1920x1200 there's nothing significant to talk about. World in Conflict is likely more CPU-bound than anything.