I have the DR, and the center sharpness IS kind of incredible.
To say that the DR has the edge over the hex in terms of build quality doesn't mean that the hex is not well built. On the contrary.
I have a couple of Hex's, and they are probably a match for current Leica production (some say better).
That being said, if I had to choose to have only one 50, I would go for the Hex for two main reasons:
The minimum Focus distance is .7m while the DR stops at 1m.
The throw is shorter on the hex.
I think the weight is also a pro for the hex.
So overall, for my type of shooting, I would go for versatility, because the drawbacks are really minimal.
If I was shooting BW portraits or landscapes, I may have switch the choices.