So bottom line is single 7970 is behind, has far less features, costs more in the USA, has questionable drivers in comparison, and only in half or less of the games at extreme resolutions with unplayable frame rates does it produce anything that can possibly objectively be called frame rate equality, and that at unstable overclocks nearly no one is really going to keep cranked while playing...
There's really not much more to say about the matter.
I cannot see a single real 7970 advantage except amd made it and nvidia did not, which is a huge emotional advantage for more than are willing acknowledge that.
Trying to prove nvidia doesn't know how much ram a certain potency of core at max resolutions is in need of has proven a futile and humiliating exercise with such a large urban legend lore backing it, no doubt more experiments will be spoken of even if the data is somehow ephemeral and phantom like or somewhere off in some non existent future..
I read again, all over, "the game may materialize in the future that takes advantage of such a thing" - this right in reviews that solidly conclude at 2G (or 3G) ram limitations frame rates are already toast for playing before hitting any wall - but they of course have to say it - like last time, and the time before, and the time before, and before and before.
If someone shows one or two games where they can achieve the dreaded and completely absent scenario more power to them, they will have the achieved the equivalence of the one or two games PhysX is put down for, only less so, and unplayable to boot, a defeat in any objective view.