The latest episode of Linux Luddites (ep. 65) has a 20-minute review of Ubuntu MATE for the Pi 2, where they compare it to Raspbian Jesse. I enjoyed their insights, and I've become a fan of their show. Note: One of their hosts, Joe Ressington, also does "The Pi Podcast".
Spoilers (you've been warned):
- One host felt Ubuntu MATE "edged" ahead of Raspbian Jesse. Another host even "forgot" he was using a Pi 2 while using Ubuntu MATE (which is to say, it felt like using a "real computer", in the sense that it was only noticeably sluggish for him in a couple of situations during his review).
- They appreciated how Raspbian Jesse automatically resized the partition to take up the whole SD card, upon first boot, and you didn't need to go through any sort of new user account setup, before getting to a working desktop (on that first boot). Ubuntu MATE does things somewhat differently when you first flash it and start to use it.
- The speediness of launching and using apps seemed almost exactly the same in both distros.