Well, katana is lighter, more aerodynamic and looks really cool, so as long as you aren't fighting paladins wearing Full Plate Mail with a +3 against katanas, I'd pick it.
Maybe an European lonsword could break a katana, if you took the whole force of the blow with the blade instead of just steering it away, which could alone do some nasty things to your wrists. At least it would hurt.
Oh, and if you really are going against a mad fisherman wielding a rusty butterknife, you'll need at least a laser-guided rocket launcher, a battlemech and an imperial star destroyer. Mad fishermen can inflict massive damage. Skinning fish is great practice.
__________________
|