I’m not expert on the desktops but my evaluations since Ubuntu 10.04 I think Ubuntu-Mate 16.04 is the best thing since Ubuntu 10.04.
I don’t really care about pulse audio, systemd, wayland, etc. these “under the hood” things shouldn’t matter if they just work out of the box, unfortunately systmed & pulse audio certainly have been less than smooth roll outs and caused lots of issues (I minimize by staying with LTS releases) and I suspect wayland to be even more disruptive.
But I see lots of backsliding in the core apps, things like nautilus, gedit and totem are IMHO far inferior to what was in 10.04, and except for Totem the Mate forks have mostly saved the day.
My take on Mint18 Mate vs Mate 16.04 is with Mint you lose Gnome Main Menu which is to me the heart and soul of the 10.04 “look” as far as I can tell. I never warmed up to Mint Gnome3 Main Menu which is a double-wide box in the lower left corner like Windows7, Apparently Gnome Main Menu goes away in Ubuntu-Mate 16.10 so it’ll soon be moot 