Just to make the specs reliable both have CPU bandwidth at 30GB/s... 20GB/s is wrong.
The PS4 CPU have a link to the main memory of 20GB/s while the Onion(+) between CPU/GPU add 10GB/s... so using the two bus PS4 CPU have 30Gb/s total cache-coherent bandwidth.
The Xbone too... the diagrams shows 20.8GB/s direct link from Jaguar to memory but they stated 30GB/s because there are another bus to make the coherent-cache.
This CPU part is almost identical between PS4 and 360.







