I believe that the Xbone has already hit its graphical ceiling while the PS4's hidden power has yet to be fully exploited.
We've received reports that PS4 ports took 2-3 people to complete. If you were a managing director at a multiplat studio, what would you do? The truth is, PS4 games are unoptimized.
Xbone games, on the other hand, needed 99% of a studio's manpower to and time. You can bet your ass that all multiplat studios and 1st party studios did every single optimization trick in their books to get the Xbone version running at (semi) smoothly at 720p. In addition, the Xbone has no secret sauce like the PS4's massive GPGPU capabilities.
It's incredible that PS4 games look better than Xbone games even while using a small fraction of its power and with unoptimized code while the Xbone is using all its power (Flopza devs) efficiently.
The PS4 is a graphical monster.