i compared them to a few sets that i heard in the same price ..
so besides the m50x they beat the mdr v6 in everything besides look (doesnt matter tho.) i also find it much better then the hd280 pro....
the m40x are much more natural then the mdr v6, with better, more accurate bass, natural mids, and not piercing colored highs like the v6 have.
the m40x has less bass and more highs then the hd280 pro, also more soundstage (the hd280pro are so bad in this category, they sound canned).
the m40x do not leak sound untill 70%, where the leakage is still quite minimal.
the isolate better them mdr v6 and worse then the hd280 pro.