Here comes the science...
First, I have demo'd the AD and MD to at least a hundred people over the last three weeks. Not ONE has told me they prefer the MD to the AD. And nobody has said "wow, there's just not enough bass." Sure, someone may have thought it, and surely someone will think this, but there have been a lot of people who have voiced a clear opinion to me on this.
Why? Because the headphone is all around better. The bass is cleaner, it integrates more smoothly with the mids, and it is really fast, lively, natural and detailed.
The bass is better in every way, and you kind of have to hear it to get it. The MD has a bump from 100-180Hz or so. The bump is due in part to resonances in the cup itself, which means it creates bass that lasts too long (overhang) and blurs the details out. While there is "more" bass due to this, it is in no manner better. Further, this region is where the harmonics of the low bass are, and what this means is that while there is more bass overall, the upper bass can somewhat obscure the lower bass. Choice of music (e.g. where the bass energy is) may amplify the difference.
Because the upper octaves of bass are clean and free of resonance, the bass is cleaner and more detailed. Perceptually I concur with Matt 100%: the bass on the AD feels heftier to me because I can feel and hear the low bass without a "veil" from the upper harmonics.
Of course there are some people who will prefer the extra perceived bass of the MD vs the AD, but I believe that if you give it some time to adjust to a cleaner, faster, more detailed sound that let's you really feel and hear the bottom octaves without coloration or overtones you will never go back. Some may want to eq for fun, or fiddle with the bass vent, but most everyone who has heard them has told me they like it as is.
As usual YMMV and FWIW but I wanted to at least clear the record as to why some people appear to have conflicting views on bass quantity.
Edited by mrspeakers - 10/13/13 at 7:33pm