FYI, while the bit rate for USB 2.0 is 480mbit and Firewire is 400mbit, in reality Firewire has much better performance. It all comes down to the controller and the amount of processor required to access the device. Firewire uses DMA and adds very little processor overhead when accessing devices, USB 2.0 uses all programmed I/O and uses lots of processor power doing large transfers to mass storage devices.
I have a pair of 7200 RPM 8mb cache drives in USB 2.0 / Firewire cases, and in my benchmarks, the USB 2.0 interface had a raw transfer rate of around 22mbyte/sec with significant processor overhead and Firewire does 31mbyte/sec with minimal processor impact. I use them with the firewire interface.