It's nice to see someone giving actual explanations for his/her choice.
I just think gnome-shell (with a few easy tweaks) is very classic in use, and
very appealing. Fallback is ugly as f*ck. Same with Mate IMO.
Appeal matters for new users. But I agree that the "out of the box"
gnome-shell is not familiar enough.
There's also gnome-classic for a near-Mate looks.
But the ability to run better on slower hardware (I've read it's a very minor
issue), and that seemingly unique behavior with external drives looks nice.
According to this, I'd vote for a slightly tweaked gnome-shell as default.
New users around me are more than pleased.
A few tweaks that come to mind : Faenza icon theme (or something even more
classic), activate minimizing/maximizing icons on Abrowser, add the
applications menu, get rid of the rounded corners (I ended up doing it in
CSS), add a dock extension, and that's pretty much it, if I'm not mistaken.
I'll have to test the external drive behavior.