no one ever calculated I think, some person might gear self for speed plus piercing, and hit some prison guard for some 20k+ with just a slash because of a huge level difference.
I don't know about the armors, since I sold them and don't know those stats off the top of my head. If one of them has lightning piercing, don't get that one. That's all I know.
But usually two-handed weapons are much better than two one-handed ones. They are just way more powerful. I guess that's because you can be a little more flexible with two weapons. The only times I ever used two weapons was in Z1 :P when there are no weapons, and a speed bio (two weapons that increase speed and phys piercing, one Z4 and one Z5 one).