I came from 7970. Its an okay chip, but i wouldnt change my 680 Lightning for any 7970. It just works. I had several issues with my 7970 especially in older/not so popular games. Fx. Amnesia i got huge fps drops and GTA 4 was unplayable at high settings because of fps drops below 30. This aint happening on my Lightning. It just works flawlessly. Besides that, i had severe coilwhine in all intros/game menus, and still an annoying whine when playing games. On two different cards.
On top of this both my 7970 couldnt do 1200 MHz stable. And my GTX can do 1480/1750 stable at 1.35v. It's way faster in all the games i play. Especially BF3
Even at my 24/7 settings in sig. (stock gpu voltage)
For (most) benchmarks, im sure a highly clocked 7970 would be nice, but why compare with a 1342 MHz 680 when most Lightning do 1450+ at maxed voltages? And in 1920x1080/1200 it would be different numbers