first off,
I really don't notice any differance in printing speed with any of the ports, I use both usb, parallel, and network, all seam to be the same.
as for tying up a usb port, I would highly recommend that you use a self powered usb hub for the connections, as it will give you a greater number of ports to use and also remove any power draw from the motherboard usb supply.
I have 3 usb hubs on my system, and every thing works just great