Vastly inferior is taking it too far, you're talking about a culture that was focussed around warfare for many centuries and had the potential of being just as adept at archery as Longbowmen. But I will agree that an armored knight versus a Samurai would win. There are many variables that come into play of course, so it's difficult being absolutely sure of it. Eventhough katana's rank amongst the best swords in the world, if not the best, they too weren't very capable of slashing through European armor.
An unarmored Knight versus an unarmored Samurai however, the Samurai would have the upper hand.
There's a guy who has written a nice essay about it.
http://www.thehaca.com/essays/knightvs.htm