Adaptive armor has a base armor value, usually between 20-32, depending on the weight of the armor. After that, all of the mods, armorings, enhancements and augments you install will add to that value, so Adaptive armor does grant a tiny armor stat jump, though it probably means next to nothing in terms of playing the game.
Adaptive armor does not have any more armor rating than regular stuff. Regular shells have that same miniscule amount when you pull the armoring out.
I'm not sure about durability though.