[Rygar]

I think it really depends on how you level. If you solo a lot, I would go for ac (as hp will only help you at full health). On my monk I hit the soft cap of 120 item ac for my class (meaning the values of just the ac on my items, not converted ac in the UI... Warrior soft cap is higher), while I haven't parsed it I do notice a difference when I put on resist gear and miss the soft cap.

At low levels, a 55 or 65hp bonus should trump anything less than a 5ac gain, but I would not equip something that only gives 20hp and drops your ac. I would not worry about stamina as those bonuses kick in much larger at the end game.

In regards to broken ac, I heard it works in calculating properly, yet it doesn't display properly in the client. That is why I go by adding up the ac on my items to see if I'm at the cap or not.