Just looking at damage numbers, it looks like the Monk/Swashbuckler gives a somewhat higher return but much less in-combat utility to assist other players, and with lower AC, whereas both the full Monk and the Monk/Fighter are about the same in terms of damage range but with much better utility and AC. How delightfully difficult: Reliability and utility versus nova potential... The roleplayer in me leans towards the latter two, just because my sense of the character is that the loss of his tribe would lead to more of a wanting to make sure the party prevails as opposed to rage-filled head-smashing...