The Myth of the Amended Return keeps popping up here.  E-filing is sort of like sending it by fax (except maybe IRS doesn't need an ink cartridge to print it out) -- it is still reviewed by at least one and maybe two or three examiners.  Mailing a paper return does save you a few days, if you believe IRS when they publish weekly reports that they are up to date on opening mail.  

It's related to the Myth of the E-Filed Original Return, which has been shown to be unreliable when IRS needs to do a clerical review of things like RRC and EIC.