In case anyone is curious, I finally managed to locate a bit more of information concerning the two grinders in question. (I looked at the NS site a few times before finding this...
GRINDER-DOSERS:
A good grinder is essential for making good coffee. Nuova Simonelli produces professional grinder-dosers with flat or tapered grinders (preferable because they grind the coffee more slowly over a larger grinding surface area, thus avoiding even minimal "burning" of the coffee). Grinding settings are "creep" adjusted by turning a worm screw which moves one of the two grinders up or down to set larger or finer grinding quality. The various models are available black. Another important distinction should be made as regards automatic grinder-dosers (which operate automatically when the ground coffee is about to run out) and manual systems (switch-operated). Lastly, given the importance of the surface area of the grinder blades in terms of superior grinding quality, distinction can be made between 65mm and 75mm grinders. The MDXA is the automatic version of the MDX; manual models include MDM, MDX; Eureka.
There isn't much info on the MDM. The only NS grinder better than the MDX (that I know of) would be the Mythos, but it's for higher volume use, takes up more space and of course costs more.
