There are three classes of armor in Age Of Gladiators II:

The accelerating tiers of armor provide increasing mitigation values, but at the cost of taking up additional inventory slots on your gladiator.
Light Armor takes 1 slot, Medium Armor takes up 2 slots, and Heavy Armor takes up 3 slots.
Mitigation & Bonuses
All armor classes have two types of mitigation values:
Energy resistances mitigate against ranged laser attacks while kinetic resistances defend against melee hits. Some armors will be balanced evenly between the two mitigation values, while others will balance heavier in one direction or another.

Due to the sophisticated and powerful exoskeleton technology of the armor, they also provide the user with a bonuses to movement and speed (action points). The armor technologies also feature vitality and organ-boosting technology, providing a boost to the armor-wearers overall health during combat (hit points).
Upgrades
Armor mitigations can also be upgraded by armor technicians. How much they boost their armor depends on their upgrading stats for each particular class of armor.

Armor technicians also require a workshop in your base from which to upgrade armor sets – so be sure to build one (I will be talking more about base building in the next few days) if you want to maximize the efficacy of the armor sets you have purchased from the bazaar.

And of course, the occasional legendary armor set can be earned from missions that you send your gladiators on.
Armor shredders are special items that gladiators can arm themselves with to reduce the mitigation values of opponent armor, so consider that as well.
Summary
So it’s no longer just a questions of which armor is the provide the best mitigation: it will be important to choose your armor based on the bonuses they provide as well.
Where mitigations also become important is in matching your gladiators equipment based on the individual or team they will be facing – if a gladiator is going to be fighting a ranged specialized opponent, by all means deploy him in that 40% energy resistance, 11% kinetic resistance armor sitting in your inventory. It's pretty much worthless against melee attacks, but it will be practically impervious to ranged ones.
So strategy becomes much more important in selecting armor now more than ever before!