If I was ansering on behalf of my Scoundrel, I'd have given my vote to Corso.
Having since re-rolled a Gunslinger, I saw the light for a second time and my vote resides with Bowdaar, simply because I found him to be quite a genuinely friendly and charming companion - it also helps that he is the only not-annoying character who is not "forced" to join the Smuggler's crew (lookin' at you, Risha and Guss).