Mageia is a distribution forked from Mandriva some time ago. That’s not a secret. Also, it’s not a secret that Mandriva’s preferred desktop environment was KDE. Even the fact that the latest version Mandriva 2011 has only a KDE option proves that position.
At the same time, Mageia continued the old Mandriva strategy, and released their distribution with two options: KDE and GNOME.
I have only tried Mageia KDE so far, and had no chance to try GNOME. I finally got a chance to try Mageia 2 GNOME myself.