Xfce is the default Desktop Environment on all CLASSEScientific Linux 7 (SL7) systems.
From the xfce.org site:
"Xfce is a lightweight desktop environment for UNIX-like operating systems. It aims to be fast and low on system resources, while still being visually appealing and user friendly."
For a tour of the main features of Xfce 4.12 version used at CLASSE, please see the xfce.org 4.12 tour page.
Both KDE and Gnome suffer from NFS locking issues when the same user account is simultaneously running multiple sessions, across multiple computers. Xfce avoids thess problems, thus is recommended for both the local destop and a remote session via X2Go.
For additional notes on running multiple sessions at once, please see MultipleSessions.