A woman won't shoot a gun that hurts. And that leads us to the next difference. If a gun hurts, it may not be entirely because of the gauge. Sometimes it indicates that the gunstock is the wrong size or shape for the shooter. Slacks are unhemmed, because the manufacturer didn't know who was going to buy them, and couldn't pre-fit them.
Guns are the same way.
The stocks are made a traditional size and shape, and they don't fit everyone. If you don't alter the stock to fit you, you're missing an important step. One thing Mary looks at with her students is the angle of the buttplate of the shotgun. She says it should be a mirror image of the shooter's shoulder. If a shooter puts that gun to his shoulder, it causes him to put the gun over to the edge of the shoulder on the joint rather than where the 'pocket' is.