One place where the 7970 wins out,and it affects alot of us,is Idle power!! AMD cards have zero core(the thing keeping Tom from Quad x-fire, till he got it sorted). If you sit in front your computer messing with it all the time, it doesn't matter, but if you leave your machine on all the time or walk away from it alot, the AMD cards will sense when your monitor turns off and cut it's core power to only a few watts.
Basicaly I see this as the same thing:
Nvidia=higher base clock and overclocks when needed, always using less power.
AMD=needs more power to do the same work but underclocks when not needed, to make up for it's power wasteing