I know that one difference must be the quality of the polycarbonate disc. In the news section, Maxell was quoted as saying that at too high speeds, poorly made discs can disintegrate in your drive. What are the other differences?
The lower speed discs will usually need more heating to change, so they need more laser time per pit. If you burn them at a high speed, they don’t get heated enough, and thus do not have as clearly defined pits and lands, which can lead to reading problems.