I would discard xfce, because is similar to lxde (trisquel mini).
Being trisquel oriented to a regular user I think gnome-shell and unity are the best options. Both have the problem of 3d acceleration and I don't know how they support screen readers, which is a must in trisquel.
I'm afraid we will have to wait to see if gnome-shell can be run with more free friendly graphic cards than nowadays. I would like gnome-shell to be the default user interface in trisquel.
