The best value is virtually always the R9 280X until prices shift again. If you can find a GTX 770 for as much or less than a 280X, that's a great deal, but you usually won't.
The GTX 770 is usually a little faster, but the 280X often comes out slightly ahead in games sponsored by AMD, such as Battlefield 4. No idea what will happen with GTA V, but the two cards are pretty close in most games.