If you want best sound from wireless/ANC headphones go B&W PX...
Havent't heard 1000xm3 though.
Bose is comfortable but PX isnt uncomfortable.
I struggled between getting the H9i (which I ended up ordering, still awaiting delivery) after much, much reading on both the PX (I have the P5 Wireless, my only significant experience with Bowers & Wilkins headphones) and the H9 and H9i, and a very brief, uncomfortable listen at a Best Buy to both the PX and the H9i -- but the setup was crappy and I couldn't plug directly in to either headphone, so I don't think I got the best comparison between the PX and H9i.
I was surprised after reading about all the comfort issues various folks have had with the PX that I found the PX to be quite comfortable (granted for a very, very short demo) and I liked that it felt very secure on my head.
But I just couldn't be certain about the PX and having had experience with B&O (1st gen H6 and for a very brief period the H8i, but the small ear pads hurt my ears very quickly), and the fact that the PX can't be used truly passively (requires power even when using 3.5mm input), I decided the H9i made more sense for me.