I put the QC20s up against my favorite pair of in-ears, the B&W C5s. These are $120 less than the Bose, and not noise cancelling, but I think offer a good baseline given that I love their sound (they’re also very well reviewed and measure well too). The C5s have a lot more bass than the QC20s (probably even a little more than is strictly “neutral,” but I like that). The bass is also a little “tighter.” Bass drums sound a little more realistic, for example. The treble is more open on the C5s. Snare drums are a little crisper, but without any real boost to the same frequencies the QC20s do.

So compared to my “reference” headphones, the QC20s don’t sound quite as good, with less bass, and aren’t quite as open sounding. However, if the C5s are an A-, the QC20s are a B/B+ overall. Since the noise cancelling on the QC20s is easily an A+, the fact that they sound good is practically an added bonus.