im not sure you will notice the difference, but if its super critical use firewire, it has increased to 800 Mbps with 1394b. With optical cables, that can be bumped upto 1600 or 3200 Mbps. usb is best for low-speed devices 1394 has its advantages speed/distance, headroom, and simplicity etc but best not to worry to much ,..and neither usb or firewire will help he benchmark his drive to see if its running full whack
