I got the QC35. I also have the Sennheiser Momentum Wireless 2.0 (AEBT), already for about 8 months.
I bought the QC35 because the AEBT put a painful pressure on my left ear after 1-2hrs of listening and because I the 2,5mm jack is recessed, which prevents me from using a 2,5 > 3,5mm adapter to plug a boom mic (V-Moda Boom Pro mic).
Subjective aesthetics and sound quality points aside, these are my observations when compared to the Sennheiser:
Pros:
- More comfortable
- Better noise cancelling, though not much better but I'll take all I can get. Test conditions: I have a school next to my office and have kids talking loud and screaming all day long. This gives an impression of performance with random human voices. I also have a fan to give an impression of constant noises (representative of an aircraft sound).
- Folds into more robust and compact case - I’m happier to carry the Bose around compared to the Sennheiser
- Ability to manage paired devices via the mobile app
- Compatible with 3rd party 2,5mm jacks, unlike the Sennheiser (unless you hack it, but still limited to hole's width)
Cons:
- Can't use NC while charging. The Sennheiser work while charging which is a big plus for me. Now the Bose will give me charge anxiety
- Passive wired performance not as good as active. You feel it immediately in the bass. The Sennheiser offer no shortcomings when used passively on wire.
- Noise floor noticeably higher when active. To me this is only a con because they make it more noticeable you’re wearing the headset when not playing music (useful when you just want to cancel outside noise). I have to pay attention in order to feel the little noise that the Sennheiser make when active (but not playing).
- The Bose noise cancelling make this weird air/sound pressure in your ears. The Sennheiser have none of that.
In terms of other functional aspects, they both perform similarly.
BT connection cracks and dropouts are the same with my MacBook - that is to say the Bose will also crack here and there and range is not great. Much more reliable with iOS devices, like the Sennheiser. I think there's nothing that Bose or Sennheiser can do here, you're basically dependent on the quality of the paired device's BT transmitter.
I was pleasantly surprised to know that the Bose support AAC as opposed to AptX like the Sennheiser. I prefer AAC since that’ll give the best quality on iOS devices, which are otherwise limited to SBC. Both headsets had to somehow be forced to use the higher quality codec in macOS. The Bose required AAC to be explicitly enabled in the Bluetooth Explorer utility. The Sennheiser have to be manually connected via the Bluetooth menu (as opposed to automatically connect). This is another indicator of how much Bluetooth sucks with Mac hardware and software.
Sound quality-wise: Sennheiser are more balanced and have more pronounced bass. Normally I favor better bass, but the Bose are still quite good and have noticeably more detail to my ears, especially in the treble area. I’m enjoying the Bose more than the Sennheiser.
I'm not gonna go into aesthetics since that's totally subjective. Both look and feel good to me in their own way.
Conclusion:
If I didn’t need to connect the external boom microphone and if I didn’t have the issue of discomfort with my left ear, I wouldn’t even have thought of getting the Bose. As it is right now, I think these are two competent headsets and would say it’s a tie. Not for sound quality (difference is subjective at this level of quality IMO), but for functionality and for the noise cancelling experience.