HIS HD 7770 vs GTX 460 - Curiosity not advice

Hey guys

This is more a curiousity question and learning about hardware rather than a "which card to buy question" , i actually own both cards, recently purchasing the HD 7770 from HIS 1Ghz edition

Now my question is, what about the HD 7770 is it, that makes it feel smoother and perform somewhat better than the GTX 460, the stats are quite equal, i didnt get much of an fps boost ( i dont care, i didnt buy it for better fps, i bought it to have a spare card )

But yet, gameplay, and movement, shadows, and AA feels so much smoother in general gameplay while gaming in any game ive tried

the guy at the store said something about "new generation" and "new chipsets making it perform better", and as i said, i wasnt after a better card, im happy with it. i just wanted to put my 460 away before its overused xD