The "speed" of a scanning process is dependent on many factors other than the USB interface, it is hard to say because each specific setup of computers / scanner / images / software just varies. That said, USB2 is probably not the bottleneck, as the DSP that handles the image processing on a scanner is ofter slow, not to mention the mechanic movement of the light and sensor etc takes time. Also the resulting file size of the images are irrelevant, these are generated on your computer, not from the scanner which needs to be sent through the USB2 cable. You cannot think of it the same as external drive bandwidth over USB.
Anyway, I would say unless you are dealing with thousands of scans, otherwise just live with what you have. A proper scanner and dedicated computer workflow that "really" speeds things up is not at consumer price point, they are for libraries or museums etc. If speed is still a priority, try to optimize the scanning settings to the point where you can accept the quality, while it takes the least time to process.