Well it could be more laggy, or the person doesn't know how to port forward. It's quite easy for me, just searched around youtube for a tutorial. All you have to do is just change online-mode to false and put your server-ip your localhost's ip. 192.168.1.(1/2/3/4). But you'll have to give other people the public ip to join. But you'll have to use your localhost ip for ONLY you to login.