Like Killerx said, the 7850 overclocks VERY well. I'm not even overvolting, stock clockspeed is 860Mhz, but I can get to 1100Mhz with certain tools like Sapphire Trixx.
But yes, without overclocking the 650 Ti boost is faster in most cases (I believe 7850 is faster in FC3 though). Another thing, and I don't how much it will help, but the PS4 has an AMD gpu so in the future, games will probably be a bit more optimized for AMD cards.