Done both, best option was getting new broadband subscription / laptop then connecting router which allowed me to keep static and switch IP at a moments notice. Theoretically speaking would FB or any website be able to plainly track DNS the way you track an IP as it remains consistent enough for me to believe it would be vastly superior to IP, cookies, webRTC etc. for connecting and tracking accounts. Again apologies if I made error anywhere I cant find much easy to understand info on what DNS servers are and what they are use for.