The windforce edition of GTX 770 is not available in India and surely it will be priced 30K+ when available. Now the thing is it might perform better than HD 7970 GHz edition or a normal HD 7970 clocked over 1000 MHz but the thing is how much performance improvement you will get. Most of the reviews haave shown it is maximum 4% in some of the games and for rest of the games either they are equally matched or 7970 has some small advantage. Now for 3 to 5 FPS higher, if you're willing to pay 3 to 4K extra then get the GTX 770.
Regarding overclocking, recently Hardocp has performed a in depth review of the three cards, GTX 770, GTX 680 and HD 7970 GHz edition. They overclocked all the cards to their maximum level which is around 1250 MHz and on that speed, all of them actually performs similarly.