I own both. I have 1a for over a year and use it daily in the office and now I upgraded my old bluetooth headphones to MDR 1000xm2. It's been only a week so some burn in may change the sound a little but this is what my feelings are about the both. 1a sounds very pleasant, with deep but not overpowering bass clear but not over the top high and well controlled mids. It is extremely light and comfortable to wear. Sometimes I wish that all my audio (in the car and at home) sounded like 1a. It's certainly one of if not the best (IMHO) sounding headphones I tried. Now to the 1000xm2- on flat (in headphones app) settings- it sounds really well controlled. The bass is not as mellow as 1a, but still present, probably a tad firmer. The mids are really good and well controlled, the highs are well defined but do not hurt your ears like some other headsets. The ANC is amazing and does a great job canceling most of the noise. I can hardly hear my keyboard clicking when I type. Maybe with some playing around and burn in I could get the sound close to 1a, but I think the sound profile is a bit different- more precise and flatter a bit closer to what you would expect from monitor headphones. So in my personal taste 1a sounds more pleasant and I will continue using it in the office and at home where being plugged in and having no ANC is not an issue. For town, train, plane etc 1000xm2 is really good, and if I had to chose one I would probably go for 1000xm2 due to versatility. It is not as light and slightly less comfy, but those are small trade offs for great bluetooth connectivity, long battery life and amazing ANC coupled with great precise sound. So all in all, if you already own the 1a, I am not sure it would actually be an upgrade if you replaced 1a with 1000xm2, those a quite different headphones serving their purposes very well.
