Has anyone found a good benchmark comparing the 4G 770 to the 2G ones? I feel that 2GB will be a little light next year or the year after, and seeing that the Gigabyte 4G cards are only about $50 more I would seriously consider it.
There isn't an appreciable performance difference between the two, as most benchmarks focus on single screen resolutions. What 4GB will allow, however, is higher resolutions with higher AA levels and no compromises in terms of textures and game assets.
Are you playing at 1080p? If so, 2GB is fine. 4GB will not offer more performance. 4GB may make sense at 2560x1600, and will make sense for surround. As mentioned, benchmarks won't show a difference, but having only 2GB especially for surround will limit your in terms of image quality options. That being said, if you're looking for a GPU to hold onto for a year or two the 4GB card may make sense even if you're not using surround, since games will be more demanding starting this holiday season.