This was taken from the Crutchfield description of the 800M2:
The ultimate disc drive
Want to dance around to your Super Audio CD collection? No problem. If it’s a disc, the UBP-X800M2 will almost certainly be able to play it.
I thought the Sony 700 could handle SADC but not DVD-A. I don't have discs of either type to test, but I could have sworn it could do one but not the other whereas the 800MS could do both.