Agree on the durability of the M50s. Have stuffed them in my backpack and carried back and forth to work, on trips, etc. and have really held up. Good construction and really feels like PRO quality in this regard.
Harder to say if they have the sound you want. I really like their versatility across musical styles. I auditioned them at a local guitar center store and selected them because I liked how they did the sound of guitars on rock music. Not a headphone that I'll ever let go, but definitely not for everyone. Nothing to speak of in terms of soundstage, for example.
Also the cord is long -- which is maybe great for a studio environment but always a hassle when you're walking around.
Will you mostly be using out of an iPod or similar player.