Armor Levels

Alright, so hopefully someone understands this a little better than I
do but my question is simple, is there a hidden armor class for armor?

Multiple times I have piced up items with roughly the same stats except
one is a lvl 20 tattered robe and the other is a lvl 30 tattered
robe... Which one is better? The stats listed under the items look the same.

Is there some hidden armor class rating that I am just missing out or are the items really identicle.

Sorry for being dense

Nope no hidden stats as far as armor goes. You'll very likely see some level 20 blues that have better stats then level 50-60 armor. Its just how it is. Go off the stats and not really worry about what the level of the armor states.

This also applies to armor types. You can find Light (or even Cloth) armor with better defense than Medium armor. This won't be the case with even-level items, but some times it's so insignificant as to be irrelevant. I have Medium Armor blue boots that add stamina, a bunch of invulns, and 0.3 defense. Next level I'm switching to Light Armor boots that add Stamina, Dex, better invulns, and 0.2 defense. I'm not exactly giving up a lot of protection, here.

it's my hope that some of this will be remedied when they start expanding the armor drops. i fully expect that all the armor you see on npc's will eventually be available in-game, and presumably most of it will be better than the 'basic' armor we all have now.

I'm pretty sure the armor type and the defense rating are two different things

Like everyone else said go with stats and not level. Also be prepared for the patch that fixes inserting gems into player made items. These sets of armor and weapons will be much better than what you will generally find off most mobs. Hopefully they will fix the gem problem this Monday June 9th.