I'd recommend going Firewire... USB works but Apple support for Firewire, particularly WRT OS installs is far more comprehensive. Also, depending on the age of the machine, you might not even have access to a USB 2.0 port. In that case, FW will be much quicker. FWIW, I've been down this path with a circa 2001 iBook - USB 1.0 ports and a first generation FW port. The USB is so slow it's insulting! I have successfully used all manner of USB devices, including DVD burners and external harddrives, though.