you are giving weird advice, usb = transfers data, firewire = transfers data
there is no compression or loss of quality happening before, durring or after the transfer that has anything to do with USB or firewire.
the only good thing that will come out of using firewire instead of usb2.0 is that you get to wait longer. that is the absolute only difference. this is because firewire is slower than USB. perhaps you had a usb video input device, in which you played your videos through it and recorded it with terrible terrible software and thats why it looked horrible. that really is the only possible scenario in which one might think usb looks worse that firewire. usb doesnt "look" anything... nor does firewire. digital data is transfered along the cable thats it.