Take your pick. Which do you really prefer? In terms of convenience, the fax machine is the best option. Why? Unlike a computer, you do not need to boot it up and wait until the operating system loads. Then you would have to execute the fax software and wait for it to initialize. With the fax machine, you lock and load. Each person has their preference, but in the end it really boils down to what one can afford. Fax machines are not expensive in the true meaning of the word, but if you are looking for an all-in-one you will have to fork out lots of money.
There are many persons who have a fax modem in their computer. In fact, it has become standard to include one in computers that are manufactured. This could serve as a backup in case your fax machine breaks down. Anyhow, it is all up to you. There is no hard and fast rule where that is concerned. If you got the dough, I would suggest that you get the fax machine. Otherwise, the fax modem works just as well. Just make sure you have a printer to print the documents you receive and a scanner to scan them to be sent via the fax mode. Kinda tedious, isn’t it? Get my drift?