Xbox One has 32mb of ESRAM that increases the max bandwith to like 208gb/sec compared to the PS4's GDDR5 RAM that maxes out at 178gb/sec. This is overlooked by everybody who is just looking at the specs of both machines.
But it is very complex , much like the PS3's cell architecture. PS3, in theory, was said to be the more powerful system, but the complex nature of the architecture proved to be a hurdle that could not jumped by many developers.
I have been on a lot of developer forums trying to educate myself on the new systems, and it seems the similar concerns that were their with the CELL processor are their with XB1's architecture.