It's not either/or but as well as
I have both and both have their individual merits.
56 f1.2 has the faster aperture but is also bigger and the AF is pretty slow compared to the 50 f2 (used on anX-Pro 2).
The 50 f2 is very good optically, is much smaller and lighter, has WR and the faster AF. It is also better for using with the OVF due to its size. And don't forget the angle of view is also a bit different (the 50 is a bit more all purpose, the 56 a bit more Tele for portrait).
It all boils down to this for me:
The 50 is the better every day lens. The 56 is the better special purpose lens for portraits.
Having both I do use the 50 more often than the 56.