I did email updates/letters because I thought it would be quicker (not necessarily on my end, but that they would receive it sooner)... I did start out with the letter wizard on Word (thinking I would mail them) and it looked really snazzy and all, but meh... I don't think it matters. But I do know some schools are going "paperless" and wanted email communications.
I, too, have not had any results from the emails, but then again, I just sent them 3-4 days ago. But 4 schools did confirm me right away saying it'll be added to my file.
As koko said, I don't think medium matters.