If you try to leadwith your hands you will probably move them far faster than you can move your tummy. Since this is also faster than your partner can move her body, if she tries to stay connected to her hand then something will get pulled apart and this is where pain can occur. You probably don't notice how fast you move your hands. If you lead with your body, then your lead will automatically be scaled to an acceleration and velocity at which humans can comfortably move themselves. This almost guarantees a more comfortable lead.
Body leads ARE easier to follow.
And in most cases less painful. Body leads, like arm leads, can be light or strong. The size of the backstep and the body placement determines the strength of the lead. As a matter of fact the better you get at body leads the smaller your steps become. As a dancer first learns to use his body to lead, his steps will be longer and larger.