Benchmarks don't show ANY difference between 760 cards with 2gb and those with 4gb. Most people on forums will tell you "OF COURSE GET THE MOST VRAM!!! IT MAKES CRYSIS RUN TWICE MUCH FASTER!!1!11" even when that's not the case at all.
Games can and will use more than 2gb of VRAM if there's more than 2gb's to use... but that does not mean they "need" that memory allocation to run correctly, they just take advantage of it being available.
Bottom line: The 4gb cards are about $50 more. If you can afford that without concern, spend the extra money just in case it helps down the line. If you can't afford that, then don't sweat it and just get the 2gb version.
Games can and will use more than 2gb of VRAM if there's more than 2gb's to use... but that does not mean they "need" that memory allocation to run correctly, they just take advantage of it being available.
Bottom line: The 4gb cards are about $50 more. If you can afford that without concern, spend the extra money just in case it helps down the line. If you can't afford that, then don't sweat it and just get the 2gb version.