To me the whole "overall armor" value is pretty much broken.
I had some plated steel armor with quality "Superior". It showed 379 of overall armor rating.
I made exactely the same armor again with quality "Epic" and exactly the same enchantments after
I raised my level in smithing. While all individual values of the several pieces where higher, the
overall armor rating was still 379. Pretty weird.
Your armor skill adds in here too, there appears to be some cuts where you get or dont get bonuses.
My first daedric weapon created was a daedric mace. I then realized it had exactly the same damage as an Ebony mace.
I switched and made a sword. Now the Sword had actually +2 damage compared to the ebony sword.
Axes was also the same, even when upgraded.
However, when you start to have 75-80+ in the skill, the better armor type starts to shoot forward further, as the lower one have more or less peaked.