bofish,
USB ports produce bery low current. I have read that the further the distance, the less current get to the end of the cable. For that reason, I have recommended using a 3ft usb cable, when helping with Dell's Inkjet Printers.
The difference between a 2.0 and 3.0 usb cable, should maybe be a few wires, but should be compatible.
If the cable is attached to a 2.0 usb port, then you will not see a difference. If the cable is attached to a 3.0 usb port, then you may see a little faster transfer.
The longer the usb cable, sometimes you have to get a powered usb adapter to help with communications.
Rick