So thought id write some of my early experiences with the new M2 On Ear wireless compared to the M2 over ear.
On ear: Pros:
lighter
more portable and better looking (not as huge as the M2)
easier to put around neck when not listening
alcantara pads get warm, but not as much as leather
surprisingly comfortable for a on ear (big head, rather big ears here)
ANC is surprisingly good for an on ear
Feel like they can handle being tossed around
Cons:
Pads are not as soft or filled as the M2 on ear, so they arent quite as comfortable
ANC not as good as on ear
SQ lacking in the midrange (but not terribly)
Over Ear: Pros:
Over ear, less pressure - more comfortable
ANC is good, better than the On Ear
Excellent SQ (best of all the wireless ANC's I've used and its most of them)
Cons:
Bigger and heavier - I personally didn't like wearing them walking around a city
Weight + leather pads make them steamy after about 30-45 minutes
Basically, between the two, for SQ the over ear - no question.. but the on ear sounds really good 75-85% there. The on ear is a lot more portable, walking around I had no problem putting them around my neck when talking to people, whereas the over ears my neck would constantly bump into the ear pads. I like and dislike the alcantara - its cooler and doesnt have that stick when taking them off after a long listening session like leather cups - but its not padded as much so they feel stiffer and don't conform to the ear well.
In terms of other on ear headphones I've tried, the BeoPlay H8 sounds better than the M2 On Ear and has better ANC, but is also more expensive. I would say they are equally comfortable, but I prefer the look and build of the H8. The M2 is lighter and I would say more portable just because it feels like it can be knocked around and tossed around without getting messed up.
If i were to give specific merits to the three headphones I noted.
M2 over ear wins in SQ
M2 on ear wins in portability and durability
H8 wins in style and build materials
One note, something I noticed that was different from the pictures online of the on ear M2, the microphone grills on the advertising photos looked like a brushed metal color, but the ones i received were painted black (a little bit of a bummer cause i thought the stainless steel grills looked nice - maybe it was the lighting in the pics).