mplayer is great and I use it as my primary video player, but I can understand why one would prefer VLC -- it's much more friendly, even if you use the GUI for both.
Also, mplayer and VLC are helpmeets in my system; sometimes VLC can play something that mplayer will choke on, and vice versa. VLC is a valuable resource indeed.
http://www.mplayerhq.hu/design7/dload.html