I go caveman on that one. I hear their skulls were pretty thick.
Honestly I think that the samurai would be at a severe disadvantage due to equipment. The types of armour worn favor the knights and it has been pointed out that the metal of a knighs sword world generally be of a mich higher quality. So if the swords met with force Mr. Samurai could end up swinging a hilt at his opponent. Not a good look.