Pretty much what Tomm said. FireWire, uses a "Peer-to-Peer" architecture in which the peripherals are intelligent and can negotiate bus conflicts to determine which device can best control a data transfer. USB 2.0 uses a "Master-Slave" structure in which the computer handles all functions and dictates data flow to, from and between the attached stuff (adding additional system overhead and resulting in slower data flow control) Firewire is really good at fewer, larger files. USB is relatively better (or not as shit) at transferring more files, but less size. Firewire will still on average be quicker, between 20-40% quicker on lots of tiny files, and 60-80% quicker on fewer in number, but larger in size files. Hope that explains kinda, if not http://www.barefeats.com/usb2.html gives more info..