WordI would imagine you are right about the differences being minor.
The 20db switch is great. I am actually liking it with the switch down with my 4003 so I can really fine tune the low gain settings. I bought this pedal for low gain applications. I am really finding too much gain or distortion to be really distracting nowadays, but the "touch of hair" sound is really doing it for me and the MBD-2 really excells at that.