The QC15's however had far superior noise cancellation. This my main determining factor between choosing which headset to keep. The noise cancellation isn't nearly as good as the demonstration unit found at retailers would lead you to believe. (those are likely configured to generate test noise at the precise frequencies of the noise cancellation circuitry of the headphones). My test was simple, I used a couple of air purifiers (not fans) running on high that reasonably simulate the white-noise like droning sound of being on airplane. Again the QC15's were much better than the Sennheiser PXC450's with respect to this non scientific test.
Bottom line, if noise cancellation is your top priority and your willing to sacrifice a little on build and sound quality, then buy the QC15's. Otherwise, if you can live a little bit more ambient noise intrusion and want greater sound and build quality, buy the Sennheiser PXC-450.
