The M5 will get you more bang for the buck than a single reverb unit will. There will be times that you may want a different effect other than reverb and with the M5 you'll be covered. However, for not much more scratch you can get a used M9 and be a bit farther down the road if you ever want another pedal of any sort. You can still have reverb running while 2 other effects are still available on the M9. All the reverbs are very adjustable as well.