Can I get some info?
I'm leading on Kambei but I can see Raiden winning, Kambei sliced in half a gigantic ship that housed thousands of metal gear sized samurai mechs as well as easily block attacks from Kikuchiyo bare handed (A robot samurai who was capable of lifting and entire support structure for a collapsed street.). They should also be about equal in speed but Kambei did easily slice lasers in half and Raiden has had trouble against slower people than kambei but when it comes to skill I give it to Raiden, Kambei may understand the sword better but Raiden can use almost any blade with just about any part of his body, Kambei can also read an opponent's movement as well as use the environment around him to get a win. Kambie was also capable of fighting against the Nobusari army for days on end with no rest and only a few bowls of rice, in MGS4 Raiden was tiring after fighting a group of assassins (Although he lost both arms at that point.) But Riaden is definitely more durable and can take more punishment than Kambei.
I lean towards Kambei due to being a smarter fighter as well and being quite a bit stronger and almost faster than Raiden. But it can go either way.