USB vs FW400 for iMac G4 external backup drive? I am setting up an old iMac G4 running Mac OS X 10.5.8 as a computer to back things up from my network. I.e. it uses SSHFS to mount network shares and back up their contents (about 120GB) to a connected external LaCie rugged hard drive (the iconic orange one).

The hard drive has USB3 and FW800, both of which are not present on the iMac. However, I have a FW800 to FW400 adapter cable, and the USB3 cable works with the iMac's USB port (which is USB2 right?).

My question is which one will be faster? Does it even matter whether I use the USB3 to USB2 versus FW800 to FW400 connection? Thanks!
Firewire 400 will be considerably faster than USB in this case, as FW has its own dedicated chipset, whereas USB requires CPU time and shares its bus with all other USB devices.