most of the time, slowest = shortest, but not always. the implication here is generally, if you can reach it with a putter, throw a putter, if you can reach it with a middie, throw a middie etc. vs. trying to throw a driver every time outside of putting range.
the thing with slow, gliding discs is that even when you are off, you are still kind of close. faster discs get bigger kicks off trees, and are much more succeptable to overthrowing, big skips, etc.