Smplayer is just a front end for mplayer, but it allows you to conveniently do many things that mplayer alone won't do, or would only do on command line.
Currently vlc will not install on my system, there is a missing dependency that I cannot find anywhere.
Also the WMA codec does not work properly, on mplayer, smplayer or kaffeine. The two audio channels cancel so there is very little sound and of poor quality.