Thanks for posting those results convexion
I assume they are both SLI results? If so could you try in single card mode please. Apparently Sleeping Dogs is not scaling well in SLI and in fact as a gaming evolved game it is not good a good tool to compare Nvidia hardware. I suggest trying a more common and more stable game with a confirmed working SLI profile to get a more accurate comparison between your 660Ti SLI and GTX 680 SLI setup.
Even if you don't post the result here at least you will have a better idea for your own reference
Actually I disagree, Sleeping Dogs seems to scale very well in comparison to some other stuff I've tried like Dirt Showdown and even Batman AC doesn't go to full utilization even with the frame limit cap removed. Maybe this isn't well known yet, but to get Sleeping Dogs scaling well you need to use NV Inspector and change the SLI compatibility flag to 0x084010F5, the flag NV is using by default is borked.