i second all the above and have both installed, but prefer gnome for no technical reason. however with your question i think that kde *might* be better supported to some extent given there is the pcbsd team and users (not that gnome is lacking). i mean besides the freebsd-kde team, there is the pcbsd team too who rely on it, if that's safe to say. (they even granted a build machine to the freebsd-kde team a few months back.