Summary: Along with the summary below, I have posted a Youtube video review of the XB900. If you like the video, check out my channel for more reviews :)
The XB800 has a very chunky design which looks pretty neat and offers high isolation. It is also easy to adjust and folds up into a nice compact shape However they have a very high clamping force and are somewhat uncomfortable.
Pros: Bassy, nice design, high isolation, folds up compact
Cons: Plasticky build, very high clamping force, not very breathable, difficult to wear around the neck