On an old SGI Indy (mips architecture) mpg321 also uses about 90% of the cpu whereas ogg123 is just around 60% You could also try using different mp3 players, maybe they use different code to play mp3s. Also try differnet bitrates. Decoding a 320 kBit file certainly uses more CPU than 128 kbit files.
Greetings, Erich
