More Interesting Armor

I made a spreadsheet that allows you to calculate how much damage you will take if you are hit by an attack of known strength, and you are wearing a set of armor with a certain number of armor points, a certain number of toughnenss points, and a certain number of enchantment protection factor points (EPF points).
Vanilla values are found on the armor wiki:
Long story short, due to toughness mechanic, diamond armor has vastly superior protection. It's not just 80% versus 60%. Diamond armor with no enchantments offers 71% dmg. redx. against an attack possessing 9 attack points (a skeleton in hard difficulty) whereas a full set of iron with protection 1 on each piece offers only 51.28% dmg. reduction, and even with protection 4 on all pieces of armor this only becomes 79.12% reduction. 

At the same time, there is no point in ever using leather, because it's easier to get 24 iron ingots than it is to get 24 leather in the early game, gold is in a similar boat, and chain... more of the same.

I propose we give armor some more differentiating unique aspects. Like for example, maybe you can move a bit faster in leather and chain than in any of the others, maybe iron has a few toughness points (more than 0 but less that 8 for a full set) and maybe gold has access to higher level enchantments. Not just an easier time getting high level enchantments, but actually has access to higher level enchantments.