The real question is damage to the fighter getting hit.

Lets say you get hit bare knuckle full in the face, you're gonna go down right? NO I hear you say! Jee you guy's are tough!

But if you were being smacked in the head with a big pillow, which doesn't actually hurt but is rocking your brain from side to side this would surely do more harm over the course of a fight? I have never fought with 6oz gloves but my gut feeling is that they would protect boxers from serious brain injury more than the 8's even though you might lose a few more teeth in the process!