The theme for this release has been adding new functionality to the MATE Desktop while maintaining the look and feel that we all know and love. While all the added features are surely quite exciting we also did not forget to do tons of bugfixing, modernising the code base and optimizing the performance.
MATE is one of the two great alternatives for people who find GNOME 3 and later unpleasant (the other being Cinnamon, my DE of choice).
So I know at one point in time the main difference between Cinnamon and Mate was GTK+2 vs Gtk+3. But then the one that wasn’t on 3 upgraded. So I am no longer sure what the differences are.
I don’t mean this as a troll. I use Gnome and aware if the history (just can never remember which decided to hang back, and use older frameworks until it no longer seemed logical (everything has been ported by now).