I never watched Enterprise, but from the screencaps I saw, I liked Mirror Hoshi. HOT!
I also liked Seven of Nine, of course. And Major Kira & Intendant Kira. Fuck, it was hot whenever the Intendant would go up and flirt with "our" Kira. Lesbian tension with the same person...only in Star Trek (and Buffy).
Jadzia was OK, but I always found her kind of boring.