FW 400 moves data faster than USB 2 High Speed even though USB 2 nominally has a higher bit rate. The reason is because USB 2 has a LOT of overhead so you have to send a LOT more USB bits to move the same amount of data. FW 800 is a lot faster than FW 400. I ignored USB 3 because your iMac is not USB 3 capable.
Is it fair to say that at today's date a USB 2 device
may be preferable to a FW 400 device for some users because it will be compatible with a potential new Mac that will have a USB port but will require some sort of interface to enable a FW device through its Thunderbolt port?
