If you are after tightly cropped head and shoulders style portraits all three are not ideal. All three have great lenses. The mamiya 6 is my favourite of the three! Although I would say the nicest medium format rangefinder for portraits is the Plaubel Makina 67, it has the fastest lens, and a really great look to it. It's also very compact for a 6x7. Another benefit of the makina is that Plaubel in Germany still service the cameras.