I know the Air is not geared towards graphics, but if it is of the slightest importance, I can say that the 2.0GHz processor vs 1.8GHz processor makes a lot less of a difference than 4gb vs 8gb RAM in most games. (Starcraft being the only exception so far).
It's not because games use 8gb RAM, but it's because with 8gb RAM, your available vram goes from 384mb to 512mb. And that makes a big difference. (I can personally verify this since my friend has an equivalent model with 4GB RAM (both brand new) and we've compared the two side by side).
Just throwing this out there since I was really close to going for the 4GB model because I don't usually multitask a lot of apps.
It's not because games use 8gb RAM, but it's because with 8gb RAM, your available vram goes from 384mb to 512mb. And that makes a big difference. (I can personally verify this since my friend has an equivalent model with 4GB RAM (both brand new) and we've compared the two side by side).
Just throwing this out there since I was really close to going for the 4GB model because I don't usually multitask a lot of apps.