Both the R9 280X and GTX 770 trade in games, depending on how well the game is optimised for each card is how well it will perform, generally i would go with the R9 280X as even if it loses overclocking will reach or even pass the GTX 770 in games and also the R9 280X can be alot cheaper, also the 3GB of VRAM will help in games like Battlefield 4, Crysis 3 and Watchdogs especially if you play at high settings and when you play Ultra with another card it wont stutter as much