"Katana vs European sword" is the sword nerd's equivalent of 9mm vs 45 ACP. They always argue back and forth about which was better. Such arguments are pointless since both types of swords were developed in the context of their respective types of warfare against armor designed at the time.
If you just look at the katana, it loses half the techniques available to double edged blades. This probably doesn't matter in the course of use by an expert swordsman. Japanese swordsmen treated their swords very differently due to the low quality of materials. This is borderline religious reverence. Conversely, in Europe where iron and steel were common, a sword of war was treated as a tool to be used up unless it had some sort of sentimental value. You'll see this reflected in techniques; the Japanese never met edge to edge while the techniques of Fiore, Liechtenaur, etc, including "winding" which would notch the edges. But, this gives the wielder access to techniques to control the opponent's sword while stabbing.
Targeting is very interesting with the katana. Since its curved shape makes it an amazing cutter, targeting seems to be more oriented toward that. Obviously, stabbing does occur as the katana has a point. But the martial arts side of it targeted eyes, palms of the hands, leather straps on the armor, arm pits, inside the elbow and so forth. I noticed the targets are very small and require precision to hit.
Contrast with Europeans: they take the fighting in close with a hand on the blade for control and a hand on the hilt for power. Perhaps JSA did this too; it's very hard on the sword. The techniques are very interesting and I'm sure there's overlap in the Japanese Sword Arts (after all, everyone has the same body more-or-less so the techniques will revolve around that). I've never witnessed a demonstration of JSA sword fighting in armor, but both styles will have Ju-Jitsu like moves.