Frankalll :
ASUS offers a better deal with 4gigs and 10 dollar more expensive. I would not buy a 2gb card in 2015.
I would like to put this idea to the test. I've reviewed several 2GB cards (which by the way perform just fine at thier intended resolution), but I've never tested a 4GB card.
Personally, I don't believe that a 4GB GTX 960 will be of any benefit at all unless running in SLI.
the only game that I've seen use more than 2GB at 1080p is GTA 5, and I'm not convinced that the GPU would be able to keep up in settings high enough to use that much memory.
The idea of wanting more than 2GB of vram makes sense, but only if you have the horsepower to make use of it.
Again, I have not had the chance to test it for myself, but I really don't think a GTX 960 has that much power.