I would take, then, Credence for two reasons:
1) you won't hurt people's ears in the class (this'd happen if you play Serenity).
2) credence is shorter, really melancholic, you can refer to the whole concept of the MAYH album, and it's kind of more accessible (more people will like it, and you won't feel as angry. What I mean is it happened to me that I played a song I really liked in front of the class, and the people there didn't give a shit about it: this is, believe you me, a horrible feeling)