Exoticus has the same music as the bonus stages. That's probably why you're confused.

As for my favourite: I really can't decide. The music is one of the top reasons why I like JJ1 so much, tons of planets use some pretty neat music.

Regarding the poll, I'd like to hammer on an insignificant detail, this detail being that Holidaius 1 and 2 have the same music. 3 is the one that's different.