Personally, I also like the Beyerdynamic DT 770 Pro 80 Ohm (Over-Ear) better. Whereas I have the open Beyerdynamic DT 990Pro (Over-Ear, Black). Open feels more pleasant in my opinion, just more open ;-) If you don't bother anyone with them.

I own both headphones and like the sound of the dt770 better. The M50x are a bit smaller, easier to store and have a replaceable cable. If the headphones are to be used at home on the computer (and there is no cable-eating cat around), I would prefer the Beyerdynamic. If in doubt, try them out.