You would get better performance from the 670s, but if you plan on having a multi monitor setup, the extra vram might be worth it for you. I would choose the 670s from these options, but you could always get 7970s for a bit more and have better performance.
Just remember that vram isn't additive in sli. That means that if you have 2 cards each with 2gb, you still only get 2gb of vram.