Copperband Butterfly or keep my Singapore Angelfish?

So I have a 4.5 inch Singapore Angelfish (avatar) in my 120 gallon reef tank. He is usually pretty good in my reef, and he does nip, but he usually doesn't damage anything. Well I got a really nice Trachyphillia Brain Coral and my angel has started to nip at it. Normally it wouldn't bother me if it wasn't bothering the coral. The coral is no longer extended and is reacted really tight. With the angels nipping, you can actually see little white marks were he has taken off some flesh. The coral should recover fine, it just needs to stop being nipped at. My LFS has a Copperband Butterfly that is actually doing pretty well. Its eating and is probably 5 inches. I am wondering if this guy would be a better bet for my reef? I don't mind if it nips at things as long as it doesn't take chunks out of my corals, and with its delicate looking mouth I am not sure it even could. I could be very wrong in that though. For corals I have Pom Pom Xenia, Frogspawn, zoas, shrooms, SPS (forgot name), Trachyphilla coral, green bubble tip anemone, pink bubble tip anemone. I plan on getting more LPS and a few easier SPS. I also want a few clams (which the angelfish is know to nip at). So what do you think would be the best for my reef? Thanks!