In terms of bang for the buck in MFD, the new S body promotions are pretty incredible. I upgraded to an S a few months ago, and still have my S2. I was planning on selling it...doesn't seem to make much sense anymore! The Leica store Miami is selling a new S-E and 70mm CS lens for 10,295 dollars, or 5995 for body only. That is an incredible value. It may be lower in MP than the A7rII or Pentax, but it is an incredible image making system. The lenses are better than either system's lenses, and the image quality is superb -- 16bit color vs 11+7 in the Sony, full weather sealing, a much more ergonomic body etc etc. I use an A7S alongside the Leica, and while the A7S can do some amazing things, it is a frustrating experience to use in comparison to the S. Granted, even though the body cost is much lower now, the lenses are still very expensive...but I believe they are a good investment. Depending on your particular photographic needs, it could be a good option. If you plan on working with strobes, the CS function will be very compelling, and the overall image quality of the system packs a punch that is a lot greater than the comparatively modest (for 2015!) 37.5mp would indicate.
I think all three are exceptionally good cameras, and picking the right one is going to be more about which particular specs are more important to you, rather than there being a clear winner. Ergonomics and lens options should also be very carefully evaluated, preferably in person. Personally I did not really pay attention to the S system until I got a chance to handle it...then it all started to make sense! I would say a bit of the opposite about the Sony. They are fabulous on paper and are capable of great results, but they are certainly a lot more frustrating to handle than the medium format or film cameras I am used to.