I own both the 50/2MP and the 50/2 Milvus, next to a range of other fifties. I'd like to recommend the Milvus because of a range of slight improvements (vignetting, gasket...) and a big one (better coatings, can work against bright light). The price was in the same range for me, because I managed to find a second hand Milvus shortly after it hit the market !
Both lenses are among my sharpest fifties, at least in the centre. I did not make extensive tests at infinity settings, but they are very sharp wide open. Please find below a comparison with the 50/1.8 G, both at f/2. All pics are screenshots from LR displays. The Zeiss pic is on the left, as you would have guessed from the telltale vignetting.
Focussing the 50/2 (any version) near infinite takes some precautions, because of the short throw. On the other hand, the focussing action is fluid (no dry friction feeling, no slack) and rather firm, so precise focussing is possible.
Possible rivals: not the Summicron-R (slight glow, nice by the way) ; possibly the Voigtländer 58/1.4 in the center... but from experience, Zeiss tends to have the highest contrast wide open at any distance.