Both GPUs are similar in performance , but the GTX 770 comes with 3 free games. Ac black flag , batman arkham origins , and splinter cell blacklist. While the newer R9 280x doesn't have any bundles. I'm sure AMD is going to add some deals to the R series cards.
So I would pick the GTX 770. No need for 4 GB. 2-3 GB is enough , unless you are using multiple monitors , or very high resolutions
Well i am up for gaming and work, i do some minor video editing, lots of Photoshoping, and gaming in free time, for res i currently use 1080p monitor.
And as well i am working with 3d modeling program Blender