first of y'all be specific. win at what? weapon superiority? a fight? ground fighting?? a sprinting race? because the samurai is very fast. It would win in a run for sure lol.
But if its a duel or fight with weapons, Hmmm. I put my money on the knight. as much as I like samurais, knights are also legit.

Samurai definitely have the speed advantage but the knight has stronger armor. they also have a shield.
The Samurai may have the sharpest blade which is good for slashing but not stabbing like the longsword of the knight. If a sword is too sharp it just ends up chipped and dented when it clashes against another stronger blade. When put into direct combat with one another, the moment the two swords struck one another with any real force, it is highly likely that the japanese blade would shatter due to its brittleness. unless its an anime samurai sword y'know? lol.
bcuz both swords are completely made different. The katana was made razor sharp for slashing, generally through unarmored flesh, while the longsword was made to directly combat other swords, and also good for just stabbing.

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from history….A knight’s armor, weaponry, and quality may be superior to a samurai. But without pissing all over samurai and the katana, the quality and availability of iron in Japan results in significantly poorer metal for armor and blades?

Saw this on Reddit

European experimentation and a literal arms race for centuries results in powerful and effective blades and armor. The longsword is a versatile weapon designed for stabbing, slashing, and sometimes even utilizing the hilt as a weapon. But against japanese armor, which is not even entirely made of metal????, I’d imagine they’d cut right through. Also, those swords carried a lot of momentum behind them, some styles focused on the concussive force of the blade itself when applied to armor rather than the sharpness. So in contrast, the katana is a weapon highly effective at slashing, very quick but not ideal for stabbing. It’s a quick draw weapon that would probably get lodged in the knight’s armor. Just armor alone and fighting styles aside, the difference in equipment may beee great to overcome for the samurai.