Most of the MOOs I've been on (and am still on...) use this bizarre OO MOO-C language that both terrifies and fascinates me. MUSHes have the not-quite-functional-but-damn-close softcode that I both love and hate, depending on the time of day. Of the two, I find MUSHes easier to code, but MOOs are just so much cooler. I used to do MUSH coding (various WoD mushes, mostly) and have submitted some patches to the TinyMUSH team.