An electronic signature is much easier to use. For example, if you are in business, then you constantly need to sign some documents. Sometimes the townsfolk need it too. You can also save a digital version of the document later. I did this with blank w9 form. Of course, you should consult with a lawyer so that your electronic signature has legal validity.
There are none, as far as I know, however you do need to make sure the electronic signature is a legally binding one with an approved digital certificate, otherwise it just won't hold.