I've been wondering about this too. It seems like every single prediction I've seen in these threads has the xbox clocked a bit higher. I'm guessing it's just because the Xbox One was clocked higher than the PS4?
Maybe people just universally have more faith in MS to be able to design a system that can cool a higher clocked CPU?
If I'm wrong, someone feel free to correct me, because I've been scratching my head over this for a while now too.
For me it's the fact that Microsoft is already compromising to reach 3.8 Ghz on the same architecture. They would push it further if they could, a part of me thinks that they are in fact already pushing it further than they realistically can, hence the SMT compromise