First of all, if you don't have enough skin around your naval then the ring will not stay in. But an outtie belly button is harder to pierce because it has to much extra skin. Also, if it ever became infected, it could infect the internal organs. This is because a small part of the umbilical cord is still attached to the inside of the stomach. An innie naval is much easier to pierce because of  its position and it has just the right amount of skin around it. Always make sure you have a professional do your piercing because they no just where to place it.