There’s no escaping the fact that Microsoft has given the Xbox One less GPU hardware than Sony gave the PlayStation 4.
Sony gave the PS4 50% more raw shader performance, plain and simple (768 SPs @ 800MHz vs. 1152 SPs & 800MHz). We’ll have to wait and see how this hardware delta gets exposed in games over time, but the gap is definitely there.
According to their data, there’s roughly 50GB/s of bandwidth in each direction to the SoC’s embedded SRAM (102GB/s total bandwidth). The combination of the two plus the CPU-GPU connection at 30GB/s is how Microsoft arrives at its 200GB/s bandwidth figure, although in reality that’s not how any of this works.