Pawara &
Mermaid II are the more luxurious end. Pawara looks good, I haven't seen it, it's quite new.
The Junk is unique, Keith is the tour guide, I've known him for years, he's really nice guy. It was funny seeing him at the NEC.
Dayboats, I would recommend Calypso, just for the pancakes. South Siam weren't bad. To be honest, they're all pretty similar.