Regarding the Bose NC700 and the Sony WH-1000XM4 noise-cancelling headphones:
Both have good noise-cancelling.
The Bose has more control over the noise-cancelling and ambient sound levels. The Sony has more auto-adjustment.
If you wear glasses or anything similar with the Bose, you lose several steps of the noise-cancelling; glasses have no impact on the Sony’s sound quality.
Contrary to its claims, the Sony canNOT handle being connected to more than one device at a time, unless you mean to use one device for listening to audio and then have your phone be absolute primary and override every time. Bose can switch back and forth between two devices, not flawlessly, though fairly usably.
They could BOTH learn a thing or ten from Logitech, and add an additional button for device switching, and another additional button so we can use voice-assistance as advertised without having to be WITHOUT one feature or the other.
If you want to be able to use a voice assistant you will have NO control over ambient/noise-cancelling levels on your Sony, unless you have your phone and Sony app open in front of you all the time. That essentially means you can have basic noise-cancelling/ambient control OR you can have voice assistance. Inane.
The Sony likes to make noise at EVERYTHING, beeping and talking loudly in your ear to tell you whenever it has turned on, whenever it is turning off, whenever it connects to bluetooth, whenever it’s changing volume, whenever ANYTHING. There is no option to stop this. The Bose can be asked to be more subtle and decent, and is elegant about this.
My limited experience with Sony’s customer support so far has been that they don’t really care about the customer and their results. My repeated experience with Bose’s customer support is that they are consistently ultimately sincere in striving to resolve issues for the customer.
TL;DR The sound through either of these headphones is fine, solid noise-cancelling, fairly comfortable, the software has notable issues and my user experience with both has been frustrating; UX a bit worse with the Sony.
Update, seven months later: I’m definitely not happy with either of them, though I enjoy several parts of life much better with good noise-cancelling headphones on. If I had to do it over again, I would choose the Bose for slightly better UX and significantly better phone calls (particularly for the experience of the person on the other end, blocking out unwanted background noise on my end).