Necrotic armor vs Tormentor's armor.

Why on earth is Necrotic so much easier to make when they appear to have the same stats? Why is Tormentor's Armor worth more? Does Necrotic have a lower resistance to holy damage?

Also, where can I find Aura of the Lich? ;P

I have no idea, but I was wondering the same about the Bonelace armor and the Fanatic's armor. Both have exactly the same stats, the only differences are

a) the name
b) the Fanatic's needs leather squares instead of tanned hide squares

Well, I guess the look is different, but if that's all...