You HAD to do it didn't you? Go and make me think; I hate thinking ¬_¬
OK, so the way I reason it is either Dalinar or Wax would fall first. Dalinar would have to rely on cumbersome and tiring tactics to wear his opponent down, considering he's fighting extremely agile opponents. Wax, as far as I can remember, was never that great at hand-to-hand combat and could be overpowered by any of the other three.
Wax would have to think strategically more than Kelsier since he can only Lurch, while Kelsier can pretty much augment himself in every way, providing temporal metals are also available to Kelsier in this match.
Szeth is the likely candidate: he's an all-round combat expert and the "perfect" assassin. Not to say that's a deciding factor, it's certainly a strong reason to believe so.
If the outcome is based solely on strategic employment and factor in a little luck, then Dalinar could come out on top. His Shardblade is a powerful weapon. But we can't forget Szeth has a Shardblade... and Surgebinding. So in a clean fight, I'd have to say Szeth.