February 18, 2014 7:44 PM EST
First let me clear up a few things...
The fight is in a level, open field with plenty of room to move around. It is clear weather, during the day, if that makes a difference
The knight is in German Gothic articulated plate, wielding a typical one- handed blade of that time period and a kite shield. He also has a lance.
While I don't know as much about samurai as I do about knights I know enough to say his armor was made of interlocking leather plates and he is armed with a katana, bow and arrow and a thrusting spear (name?).
Both combatants have the amount of training respective to their cultures and excel at the skills they need to fight. The knight practices chivalry and the samurai: bushido.
I have a gut feeling the majority are going to say samurai because katanas I must mention that the katana was not the main weapon of the samurai, instead it was the bow and arrow. Even so, the katana would have a hard time cutting through plate. Also, knights in plate did not move like robots, at least in the articulated plate our knight is in. Instead gothic knights were able to bend and stretch while in articulated plate, even into unnatural positions.
The fight begins with each combatant on foot with enough space for the samurai to get at least one or two shots in with his bow and arrow.
Also I explain your answer with fact, not opinion and sorry about the wall of text, but I did my research, the least you can do is skim. Feel free to correct me in any mistakes or inconsistencies I have made.
EDIT: The knight now has a heater shield, in place of the kite and the Samurai has a kanabo (assume he is able to carry all of his weaponry)