A quick google search of USB vs. firewire comes up with that. Seems to say that firewire is better, at least for an external hard drive. Also seems to suggest that a lot of it depends on how good the USB controller is.
IMO Firewire is much better technology then USB 2.0 it seems to scale better and throughput seems better in some cases. But USB seems to be lower cost and for general use it does very well...
I also agree that it depends on the USB controller.
Oh yeah firewire was built to replace PATA but was pushed asside due to SATA and the cost of firewire at the time... I still wish firewire replaced PATA...