45%? You're pulling numbers out of nowhere. I'm pretty sure one could push GTX 660 much further as well. They don't do that in benchmarks. And we trust the benchmarks.
And really, there's no point in trying to prove that HD 7850 is as good as GTX 660. First of all, stock performance is at totally different level. Secondly, you get many benefits for choosing Nvidia: FXAA, TXAA, PhysX, better driver support (can you believe that Radeons HD 4000 are no longer getting driver updates?).