Shields vs Armor... which is better?

I have been carrying an armor:11 shield for a while. Recently I found a Celesta that offered +30 health and +5 armor.

I tried fighting the same groups of critters several times with each item in hand; and was suprised to find that I seem to take less damage with the Celesta (taking into account the +30 health).

What does the armor rating on a shield mean, and how is it applied? Does a +5 armor bonus really surpass the benefit of an "11" shield?

a shields armor bonus only comes into play against enemies attacking you from the *front*. Thus if you have critters attacking from the back (or side) then the armor from the shield is moot and isn't being applied.

however, the armor bonus that you can get on weapon's and "focii" is all around armor, which means it applies irrelevant of where you got attacked.

I'd say you seem to be taking less damage because..

1. you have more health to start with
2. your likely being surrounded or flanked at least.. and thus the "global" +5 farmor from the focci is in place rather than "0" armor from a shield since they aren't to your "front" - this means more hits are being covered by greater armor, whereas with the shield only hits from the front were being effected by the shield armor.

and ive heard people say that choosing + armor over + health is better both is good ofcourse

If you know you're going to be surrounded [pve talk], then just walk backwards before you do.
You can easily place an entire mob to your front and your 14-16 armor shield will REALLY save your hide...