It's kinda pointless to speculate guys... Kenshin is too unrealistically powerful. The only guy in the Champloo universe that would even hope to approach him is that dude "The Divine Hand" or whatever, and he was obviously stronger than either Mugen or Jin (and would still lose to Kenshin.)
Kenshin would just do Amakakeru Ryu no Hirameki or whatever it's called and end the fight instantly.
Unless you're talking about Kenshin from the prequel OVAs, since he was portrayed in a much more "realist" light there, there's no contest.