Lemme say this,
Right now nvidia are failing badly, unfortunately.
They made a wrong decision with the 600 series 'gpu auto boost' - a noob friendly feature (like bf3)
, also the 600 series have stuttering problems right now that'll be fixed 'soon'.
So last week i just for lolz gave the 7000 series AMD cards a look over and right now at least they're the ones to beat, if nvidia sort the stuttering well fine they'll probably reign again - somewhat but the gpu auto boost is pants, the amd 7000 series is pure horsepower, controlled by the user and not by a noob feature.
Quote from TechPowerUp site:
'..doing hardcoe overclocking with the GTX 680 is boring, limited and complex.'
The 7970 windforce and the MSI Lightning are tops.( beating stock 680s in many games)
*End Rant