So you used to have an R9 280X, and now you have a GTX 770 4GB? They are both good cards. The GTX 770 has more VRAM that is clocked higher, and the R9 280X has a larger memory interface (384-bit vs. 256-bit). That's not too big of a deal, though.
I would rather have the GTX 770, myself. It uses less power, makes less noise, and generates less heat.