edit: As for how i7 4770K vs FX 8350 works with R9 280X (7970): PClab test with 7970 GE Hardwarepal test with 7970GE
But for more accurate benchies, my suggest is to wait for final version of the game. BF4 Beta is not optimized yet and you can see this from many sites that had great problems running the game with FX 6cores.
I would stick with the Intel side of things - their processors are much more powerful, and with the R280X that might cause some bottlenecking. However, I would downgrade a bit to the 4670k, more power than this for gaming seems unnecessary. This should allow for an SSD, a crucial component for higher-end PCs.
I'm not an expert in these things, so feel free to completely ignore my judgement or say it is awful.