I just tried out the QC3s for 30 days. I truly believe the noise cancelation is better than the QC2s. The big downside is that it takes some adjusting to get the phones focused into my ear canals, otherwise it let's a lot of noise seep in. Hence, if you fall asleep, it's easy to get the headset askew. Other than that, they were terrific (just not $349 terrific, IMO
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The QC2s will stay on your ear, even if you nod off.
The perfect headset would be QC3 circuitry in a QC2 housing.