Its really difficult to compare the two because they are really in their own class entirely. The Pro700MK2 has the most amazing bass i've heard (compared to the XB500, XB700, M50, and beats). After burn in the sound has easily met my expectations in terms of clarity. However, the M50 delivers in many areas where the Pro700MK2 cannot (mainly because of the bass). Highs, mids, and lows are improved on the M50, but with the consequence of much less bass. The Pro700MK2 is acceptable in these areas in my opinion. Isolation is the same on both.
Comfort, on the other hand, is an issue with the Pro700MK2. As you can see in the first picture, the M50 is recessed, whereas the Pro700MK2 sticks out a bit. The stock pads on the Pro700MK2 are terrible. The m50 pad is a decent upgrade, but its not tight and it does slide very slightly. I ordered DT250 pads and im hopeful they will help. If you buy these, you must stretch them out on something slightly larger than your head for at least a day (hopefully during burn in).
Edited by synister - 6/29/11 at 10:22am