Xfce4 or Gnome.
I sI think that in future versions of PC-BSD you want to change the default desktop from KDE to Xfce4.
KDE looks very good, but the real work is useless, but it consumes a lot of memory which is the opposite is very much needed.
Even with the effects turned off, KDE consumes a lot of CPU time and provides a fairly slow response.
Xfce I think the most appropriate choice, it has everything you need and not what is not necessary. So the same Xfce not so much integrated with the GTK library as a Gnome.
I tried to replace themselves Kde to Xfce on and turned the system on which to work.
I am on my laptop have 1Gb RAM, PC-BSD out of the box (with KDE) use ~ 780Mb RAM (no other application is running), when working with Xfce used 108Mb. This is a very big difference, given that the user capabilities identical.
Probably should produce two distributions, for example Kpc-BSD and Xpc-BSD?