I've had both the 56/1.2 and now the 50/2, I find the 56 is a more solid lens both in build and in weight although not too much more, there's much less chroma on the 56 than on the 50, there's not much in the sharpness between the two unless you really want to peep. the 50 is much more modern in feel and control especially manual focus which feels like it has much finer control then the 56. I find the 56 hunts a lot more then the 50 in low light and the focus motor is a little slower although not really noticeable. Focus distance of the 56/1.2 is as CGrieves says and the 50/2 I find is a little closer around 45cm. I've used the 56 in rain on a couple of bodies without issue so WR is a negligible benefit in my experience.
If I wasn't concerned with weight or size I'd go for the 56/1.2 although I'm plenty happy enough with the 50/2, if you get the 56/1.2 Raymond you won't have the matching set