I might say that my favorite collective style might be the "thoughtful pop" scores (I just made that term up). The scores heavily influenced by modern pop, but not like shallow pop - more like the kind of pop that feels full of life and emotion. Written with care, to develop the story. I also really love keltic music in musicals.
Having said that, I don't know if my favorite categories really line up with my favorite composers, which is interesting. I think my favorite composers, like Sondheim, Jason Robert Brown, and Dave Malloy, are the ones that don't fit very easily into a clear genre, or into a lumped category with other musical theatre composers.