I will add that if you like that compressed higher gain 80's hair metal sound that is the MRD. I couldnt get the right combination of distortion and brightness as much of the treble was tied to the Drive knob and you needed more drive to get top end. Very nice pedal, but not what I was looking for.
The DRD feels like an early 70's non-master Marshall, cross bred with the touch of a Tweed Bassman, to me. It can be gritty at 12 Volts with the drive at 10 - 11 yet stiff feel "amp like" spongy like a Tweed Bassman. This effect is more pronounced at 9 Volts. As you go above noon on the drive it saturates beautifully and gets slightly less dynamic yet kinda EVH. I seldom go above that as if I want more gain/saturation I go MH > DRD or DRD > HBOD and keep the dynamics with more gain.