Size and padding in mitts definitely plays a role. There are punchers mitts (more likely to harm others), and others for better protection. I prefer the better protection and about 16 oz like these one's I just bought RS2V High Performance Pro Sparring Gloves - Sparring gloves - Rival Boxing Gear Inc. for the bag and sparring...because less likely to hurt my hands, good wrist support and easier on sparring partners too. But for shadow boxing and things as such...use a lighter glove, closer in the weight of actually fight gloves for a familiarity, especially when closing in on a fight.