tldr; I’ve had both previous versions and I’d say get the Bose it’s your in it for the sound or the Sony if you need the features.
I’ve got the QC25 first for all the travelling I do before they released the QC35 (They launched it a couple months later) but they are the same thing except wired. Love them, the sound is amazing even with the noise cancelling and DSP off if you’re driving with something with a proper DAC. I’m using them on my desktop pc now and my sound card has a 24 bit DAC headphone amp and these things are CRYSTAL, and the profile is really deep and warm. When you click on noise canceling it puts it through an active EQ that really boosts the bass, possibly too much for some people (but probably not most). The noise cancelling is great and really cuts the drone from flights. The ear cups are big and super soft, I don’t have a problem wearing them for 6 hours at a time. The battery for noise cancelling lasts for about 15+ hours, I usually have to change them after 2 maybe 3 international flights.
But I wanted bluetooth, and had heard a good review on gizmodo about the XM2. I was really attracted to the touch feature where you can hold your hand over the ear cup and actually does the opposite of noise cancelling and amplifies the microphone picking up. I was really interested in this so I can hear overhead announcements or be able to have short conversation without taking the headphones off. But in real life this is more awkward than you think because it actually takes a couple seconds to engage and many times you need to hear something immediately. Also you have to continue to hold your hand up when it is probably easier to just flick one ear off quickly.
One advantage is if you were looking to use it in the office because it has a mode where it cuts everything except voices. So you could use them to cut down the office background noise, listening to your tunes and then if someone comes up to talk to them you can hear them just fine. (But to be polite you’ll still end up flipping an ear cup off)
The Sony has a profile with much more bass, that’s pretty well documented. The bluetooth connection and all that stuff works flawlessly. The biggest downside is the ear cups on the XM2 is smaller than the bluetooth but that was actually the main thing that was changed on the XM3. I actually get pretty sweaty and start hurting my ears after about 3 or 4 hours but I have kind of big ears and the update should fix most of that. They are also heaver than the QC25, but probably not much different than the 35. The battery life is about 9 to 12 hours. I’ve never had a problem them cutting out on me on flying internationally if I remembered to keep them fully charged when I left.
I have a lot of opinions on tech maybe I should have a blog.