I tried to get a MUC-M2BT1 on my last day in Tokyo back in Dec after I got the XBA-N3 but the Yobadashi at Shinjuku was out of stock and I don't have time to go down to Akihabara. Finally got one when they are back in stock on Amazon Japan and it arrived a few days ago. I don't have a Sony player. I use a Teac HA-P50 for my 24bit wired playbacks. I also have the MUC-M1BT1 which I got along with my XBA-A3 almost 2 years ago.
I'm mostly a casual music listener while it comes to portable music so don't expect any graph and charts. Since I don't have any wireless device capable of LDAC or 24 bit playback, all my impression is based on using my iPhone 6 playing mostly AAC, MP3/4 music and concert videos. I have include some comparison to my Teac HA-P50 using wired connections.
Let first gives you my impression of the M1.
It drives the A3 surprisingly well. I was afraid that it wouldn't have enough power to drive the A3 ( I was expecting muddier bass and less sparkles from the med and highs) but it drives them about as well as my P50. Max volume is a bit lower (but I rarely goes above 50% on the P50 anyways) but the sound/tonal quality is about the same on 16 bit sources, playing true 24 bit source using Teac app does give a more refine definition overall from the P50.
The M1 was kinda a pain to use though with just one multi function button. You have to remember the varies press and hold sequences for the different functions. The small yet firm button is hard to press and at times your press and hold will just end up turning off the device. The volume control default to 50% at startup and is also independent from the BT device you're connected to (In my case an iPhone 6) so at time you might end up having to adjust 2 sets of volume controls.
As for comfort, the M1 with the 2 cans dangling is also distracting as although they are light weight, you can still feel them swing when you move around. If you're wearing them over the neck, it's a bit better. The problem comes when you remove you earphones and have them dangling. I have had them slip off almost without me noticing.during fast movements.
In the end. Since I mostly use my A3 while indoor as they are a bit bulky while out and about, especially if you have to remove it from time to time to talk to people and they're hard to store/protect when you have them off. I end up rarely using the M1.
I mostly picked up the XBA-N3 for ergonomic reasons. It much more compact and easier to wear while out and about and I prefer a hybrid design with a dynamic driver vs an all BA design like the 300. I still think that the A3 have superior sound quality without having the meds and lows coming from the same driver like the N3. But the N3's ease of wear is what prompted me to take another look for a BT hookup solution.
Here's my impression of the M2 after a few days.
It's seems to be a bit more powerful than the M1, max volume is about 10%-20% higher as the result of the larger battery (and you get longer running time). Sound/Tonal quality is pretty much even but bass seems a bit tighter. Volume control is now linked with the output device so you only have set of volume level to worry about. Otherwise it's about the same as the M1 including the comparison to the P50 wired playback.
Ease of use. the addition of the lever type volume control makes all the difference, no more trying to remember the press sequences for varies functions or accidentally turning the unit off. There's also a English verbal alert during power up and BT connections which is nice when you're wearing the device and can't see the power/connection LED.
Comfort. Gone are the feeling that you have something dangling from your neck/ear when you move about. Feels very comfortable around the neck, in fact you won't feel it at all most of the time. I wore mine around the office for over 8 hours a days the last couple days and I kept forgetting that they were there. It's also very secure and won't slip off by accident. That have actually prompted me to start using it with the A3 instead of the N3 and I won't have to worry about it accidentally slipping off like the M1.
Basically. I'll be using the XBAs a lot more while out and about. The A3 is still a bit more noticeable so I may use the N3 on some occasions. I may even look into getting a LDAC playback device. I won't go for the ZX2 or WM1 since I'll use it mostly with wireless connections, the added cost of the more powerful/balanced output will be useless most of the time. I'll probably take a look at the A30 series.
