because it is a sword... and waaaay coooler than any of the aboveIt's been a while since one has been able to hand his sword over to a sword tester to see what kind of damage it could do to a condemned prisoner which, in ancient Japan, was just about any prisoner.
Poor attempts of levity aside, I'm a little at a loss to understand you desire to get an antique sword or self defense. I don't see the advantage over an antique cut centric cut and thrust sword of of any period of time or geographical location over a modern duplicate, though I do have to admit that I wish I had the income to allow me to collect Victorian constables' cutlasses.
Another question would be why do you think that you need to carry or keep a weapon to defend yourself with. I've lived in four states in my lifetime and all four outlaw the carrying of swords except for things like reenactments. If you did end up needing to defend yourself you a sword you might being outclassed by a firearm. If I were wanting something to protect myself with at home or one the street I would have to give one of those .45LC/.45ACP/.410 revolvers and load it with .410 buckshot. Of course, I'm not interdicted from owning a firearm where I'm at and all I would need to do is apply for my FOID card and a concealed carry permit.