I've never thought marriage really has a place in KotOR. Relationships and romance yes, but marriage doesn't really suit it.
He's not on the list but I'd pick Atton. Mandalore and Bao-Dur I could never really picture as romance interests anyway; Mandalore is too remote, devolted (and old) a figure to be interested in that and Bao-Dur is about as lively as a rotting corpse. Not that he's a bad character, mind you, but he's not the type for that.
Atton I think is a lot better due to his backstory and scoundrel-ish personality. His past as a Jedi torturer makes for a lot of potential angst in the relationship, and his Han Solo-esque character has a lot of humorous potential. Just think of the lines with the Exile's dancing outfit!
Originally Posted by Sabretooth
We will be great failures one day, you and I