* f0dder yawns.
Anyway, from everything I've seen, firewire has an advantage over USB in that it's better able to dedicate bandwidth to one high-speed device; so firewire-400 beats usb2-480.
Btw, individual disks still can't even saturate SATA-150, so SATA-300 speed only matters once you go RAID... and even then, it's only for the controller, not the individual drives, that it matters.