>>6915296longswords could be used against armored foes if it had to. much more versitle, heavier (making it useful to bludgeon) and had a pointed tip (stabbing in the chinks of the armor).
the katana has less weight, no pommel or crossguard or an effective stabbing point.
though you're right, maces, lances, poleaxes and glaves were more used than swords for this purpose.
