Subjective question, indeed.
I tend to prefer more lavish, light-hearted, dance heavy musicals that bring to mind the flashy, classic musicals of the past. Because of that I would normally lean toward a TMM.
But I also enjoy musicals with a message, as well. Those that might not be as dance-inclined, but instead focus on the music, and the message behind the music. I was moved by Next to Normal. I loved RENT. I enjoyed Fun Home.
That being said, Urinetown is the only musical I ever left at intermission. It really did nothing for me.
It's been a while since I've seen it though, so I can't pinpoint exactly what it was that I disliked about it. But I was seeing it with three friends, and they felt the same way. It just wasn't resonating with any of us.
It all depends on personal taste, and what moves you at a given time.