You'll hardly notice any difference going from a 4.2ghz FX6 to a 4.2ghz FX8 in games as hardly any of them use that many threads, so I vote GPU.
I may be wrong, but I'm under the impression that the Piledriver achitecture is substantially better than Bulldozer. (True 8 core etc). Correct me if I'm wrong. I understand that the 8350 lies somewhere between the i5 and i7?