Aiming for smaller targets like the head is kind of less than ideal most of the time anyway. You aim for the gooey center of the human, and due to the surface area and all the vitals there it's a pretty effective target even if your aim ends up off due to the situation being hectic or whatever. As for a leg, pretty good for lowering mobility and all, but it's a relatively thin target that's going to potentially be moving an awful lot.