I looked again at the specs and under the fax option, it only lists eFax for faxing.
Many households these days don't even have phone lines anymore, everyone is going with cell phones. So this is where that printer would work best. As you know, without a working phone line, regular faxing won't work so it's nice to have the Internet fax service available.
At this point, the choice would be how you personally want to fax (if you even need to, faxing is a dying format with email being so popular).
If you have a standard POTS line (Plain Old Telephone Service, - wired phone line) and you do a lot of faxing, then buying an all in one printer with a built in fax modem would be your better choice. You wouldn't have to pay for an online faxing service.
If you don't have a standard phone line or you do very little faxing, then going with a printer that uses the eFax service would be the best choice.