The MD-2 has the advantage that it can take a M-winder, Leicavit-M or a Rapidwinder. Shooting with ultrawides, you tend to shoot verticals more (cityscapes, streets etc) and it is easier to advance with a baseplate winder, than trying to use the top mounted lever.
The M1 is good too -as it allows you to use 35/50 lenses - though without rangefinder coupling.
Also consider a Bessa T as it gives you a built in meter -and a very good rangefinder for lenses that couple to it. Also much less money than the MDa/MD-2.