I like to use light gloves (12's or 14's) for bag and padwork. To me the primary purpose of the heavy bag is to increase punching power and bone density (as well as condition the arm joints and knuckles). The heavier the gloves, the less speed and power can be created. And since every action has an equal and opposite reaction, less speed and power = less resistance transferred from the bag to you = less damage = less adaptation.
I like to use them on pads as well where I'm focusing on speed and accuracy.
16+ are only good for hard sparring, imo. If you're using them for anything else, you're not getting the most benefit out of whatever it is.