In my case I couldn't use the USB port at all so I would cast my vote to the firewire. Heres a pretty good cable: http://monstercable.com/computer/productPageComputer.asp?pin=1342
Ok, like this..I have a Sony TRV33 with USB and Firewire..the USB is only for low quality video and pictures, and firewire for high quality video.. The USB doesnt have enough mbps for a high quality video. Cheers.