i´d say one must search for the lens of his taste, because there are more zuiko 50s which have something to offer -
55/1.2 has very special rendering wide-open with nervous curly bokeh, but is rather soft and takes 55mm filters which is a disadvantage. I won´t go for it unless you want to shoot wide-open.
50/1.2 has nice creamy bokeh, better sharpness and less CA, but also less character. advantage - 49mm filters
50/1.4 >1.1M sn: I´d say it´s as precise as zeiss, but with different colours
50/1.8 late MC or MIJ: some say "rangefinder-ly" sharp, I would grade it as most-sharp non-macro
50/2 macro: great sharpness acros whole frame, nice and smooth bokeh, you won´t believe your eyes how it can take portraits
personally, I would choose 55/1.2 for character and 50/1.8MIJ for sharpness