the m50 certainly offers better build quality compared with the lower level options and feel better built and are a little more comfortable with better pads. sound quality is a bit better as well but even the cheaper ones arent bad quality.
for gaming however the m50 lineup isnt great due to small soundstage. usable yes but not ideal.
i would look at the hd518,hd558,hd598 or if you like the closed back nature of the m50 and want good bass look instead at the dt770 paired with a good soundcard.