Interface speed isn't as big a factor as you might think. It's simply the protocol by which applications communicate with a scanner. The acronym stands for tool kit without an interesting name. The best drivers were intuitive and didn't sacrifice flexibility. In the end, image quality often comes down to how many dots per inch the scanner detects.
Many vendors soup up their hardware and software to increase scanner resolution.
But the industry's dirty little secret is that for most purposes, anything higher than 300 by 600 dpi is overkill. Resolution was not a problem in any scanner we tested. Correct color matching and saturation values matter far more and vary more. Equally important are a scanner's light source, optics and charge-coupled device. The CCD, also used in digital cameras, has a major effect on quality.