Get EVGA 760 ACX 2GB.
Nobody can be absolutely certain about the VRAM requirements of unreleased games but my experience with Crysis 3 gives me a rough idea on how much VRAM usage we'll be looking at from 'next-gen' games at 1080p and I reckon 2GB will be enough for maxed out graphics and 4x MSAA. I'm fairly certain that the added memory won't do you much good at this resolution.
Also map size doesn't necessarily play into graphics memory usage. It is calculated by how much information you are displaying currently on your screen and ingame drawing distances/texture mip-mapping etc. will reduce visual details over long distances. Large maps are more likely to make a dent on the memory associated with your CPU, not the GPU. It should be...