Bose 700 is better overall, but several reviews said that audio is better with the Sennheiser Momentum 3. For those who want to be different or more discerning with audio quality ;-)
From this review
After an hour listening to each pair of headphones, I started to pick up on the differences in audio quality. The Momentum 3 has a bright sound profile, while the 700 leans towards the warmer end of the spectrum. I enjoy both, but there’s no denying that Sennheiser is the more refined sonic option.
No CR or SB cash back for this category, but you can save more if you have the Amazon Amex $20 rebate offer or Amazon GCs from SB app (2%).
Edit 21/06: 15% cash back 4pm today capped at $20.
Now another $30 down (advised by Averell).
The momentums definitely sound better than the Bose, but not quite as good ANC. I suppose it comes down to what's more important to you.