Here's a
couple of articles that discusses katanas vs. longswords and knights vs. Samurai (He discusses armor, too, where European plate armor wins hands down). It's an intriguing read, since he pretty much just ignores materials used (IE, steel and iron) and looks at the broad strokes rather than nitpicking with anecdotes. He points several times at the bias against long swords that developed with renaissance ideas about swords, which were based around the idea of flimsy sporting swords.
Basically, the katana's curved blade makes it slightly better at cutting (More damage when cutting), long swords' point makes it better for thrusting (It's faster and does a lot more damage than the katana's thrust), the long sword is better for defending (More parrying).
I felt he was unfair on the Speed judgement, since the katana mostly won out because it's designed to be quick drawn and is shorter. In a real fight, having a weapon you can attack with from three points (Both blades and the tip) would make a broadsword quicker for consecutive strikes and combos, but the katana would probably be faster on the first strike. It might be a bit more complicated to code, but it'd make for some interesting combat mechanics where the katana would be great for quick one-hit-and-he's-dead fights, while the long sword would be better for prolonged fights and brawls. He touches on this when discussing versatility, which the long sword wins easily.
He leaves the matter of durability at an ambiguous tie, but I think the broadsword would win out in a contest. Katanas can be brittle along the blade, and while they do fine against soft targets they can chip if use improperly. Mechanically, I think this would translate to the longsword having higher durability and being easier to repair, while the katana would require a lot of skill to keep from damaging it and be harder to keep in good condition. We don't have item damage implemented (yet?), so that's kind of a moot point.
So, both have their strengths and weaknesses, and neither is superior to the other in all situations. I do think that it's significant that while the broadsword was a stable of European warfare and dueling for centuries, the katana was often just a side-weapon in war and a dueling weapon outside of it.
Reading through his article on
rapiers, I think I'd like to see the rapier receive a little buff. I didn't realize they dominated broadswords so hard in duels. The last time I came across one in-game I was unimpressed.