I mainly listen to rock and have the SRH440. I've heard the M50, and it's a great headphone but the mids are recessed. The SRH440 has amazing highs and mids, and have plenty of detail, but doesn't have a heavy amount of bass (I'm no basshead so I find them perfect). The M50 on the other hand, has plenty of bass, but again, has the recessed mids which might take away from the guitars. It comes down to your preference; do you want more bass, or do you want more detail/highs and mids? I myself would highly recommend the SRH440 for rock, but it's your choice.