I use KDE in dom0, it looks much better than XFCE and is imho much easier to use (type-ahead search in the start menu for starters). Also, contrary to XFCE, which is based on Gtk2, even the relatively old version shipped in dom0 has decent Hi-DPI support, as opposed to none at all in XFCE. The best gtk2 can do is scale in 100 % (!) steps.
Hi-DPI is still a bit cumbersome, especially if you switch between lo DPI and hi DPI (eg. builtin screen and external screen).