In most use cases 4gb of Vram won't be used by games. The higher the resolution of the games you are playing, the more Vram will be used. With the R9 Fury vs the 480, the Fury will get better framerates, although you might be able to bump the textures up with a 480. Also keep in mind the other issues with the Fury and it's architecture before buying it, such as it's coil whine and its high temps and power draw. If you're playing 1080p games, 4Gb should be fine.