Xbone's DDR3 has 3 times the speed of 360's GDDR3 bus.
Also, the picture is not correct, not on an ideal usage anyway, the point of esram is to isolate the biggest bandwidth consumers, not bypass it to the main ram.
Yup, you're right. I didn't notice the absurd clock speed of the 360's RAM. Funny enough when looking it up I came across a blog posting my Major Nelson claiming real term bandwidth is everything [360 vs PS3].
The picture is a simplification, but it's right. Most people are just using it as a frame buffer atm (how it was mostly used in the 360. Eventually it'll be used better to store frequently requested data, but 32GB is slim pickings in a 1080P60 HD world with advanced shaders and terrible large assets.
Some smart people will do some amazing things for it, but outside of first party titles I actually expect the gulf to widen. 3rd party devs; ain't nobody got time for that s**t,
(unless they build something into their own engines and dev tools to leverage across multiple projects)