User blog comment:B214/Shin DxD 1 discussion/@comment-32252462-20180910183143/@comment-33359929-20180914192035

I GAVE YOU THE ANSWER TO YOUR QUESTION BEFORE!!!

One's easier to mass-produce than the other.

On one side you have a prototype of a bunch of swords that probably function in the way of just taking a light-sword and adding some demonic energy to it.

On the other you have evolved versions of one-of-a-kind swords that has a will of its own, the one-of-a-kind sheath of a one-of-a-kind sword, and weapons that we've only seen ONCE (which are probably other one-of-a-kind Holy Swords that we don't know the names of yet).