Sennheiser Customer Reviews I bought both the Bose QC-15's QuietComfort® 15 Acoustic Noise Cancelling® headphones and Sennheiser PXC-450's Sennheiser PXC 450 NoiseGard Active Noise-Canceling Headphones to compare them side by side before plunking down ~$300 for headsets.

The Sennheiser PXC-450 headset is built much better than the QC15's for durability AND comfort. The quality difference can be seen in the wire gauage, battery compartment hardware, adaptor finish quality, and ear cup cushion. Sound quality was also richer and seemed more encompassing/fuller. I'm no audiophile by any means, but that is my best subjective judgement.

The QC15's however had far superior loud 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 loud 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 loud 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 loud intrusion and want greater sound and build quality, buy the Sennheiser PXC-450. Hope I can help anyone out there.
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Disclosure: I have tried all these on an airplane. I am not an audiophile. Noise Cancelation is the most important attribute to me.

The Carrying Case: All three are quite durable and stiff.
1.) Bose- the smallest, a low profile, room for an Ipod, accessories too.
2.) Sennheiser- Square shape, low profile, however not a lot of room for anything else in case.
3.) Audio Technica- Nice big case if you want to carry extra stuff (Nintendo DS, ipod, etc).

Build Quality:
1.) Sennheiser- you can tell this is built VERY well. Strong plastics, good components, thick cord. Top notch. You feel like you are getting something really high quality.
2.) Audio Technica- Nice solid construction, appears durable.
3.) Bose- If this had a Sanyo logo on the side, I would not have flinched. How can something $300 be so incredibly cheaply made.

Size:
1.) Bose- as far as over the ears go, these are pretty small.
2.) Audio-Technica- mid-sized.
3.) Sennheiser- These are big. No question, but they store flat.

Comfort:
1.) Sennheiser- Very comfortable, will fit almost any size ears. Keep on for hours.
2.) Bose- Also comfortable. I did not experience "highs" discomfort.
3.) Audio-Technica- Perfectly satisfactory. Larger opening than previous AT model.

Sound:
1.) Sennheiser- I actually wore these at home too, simply to hear parts of songs I had never heard before. Astounding. My 10yr old music collection sounded totally NEW.
2.) Audio-Technica- Well balanced, good sound.
3.) Bose- Great sound, but very heavy on the bass. I listen to a lot of rap and pop, so it was mildly annoying. I ultimately had to turn my treble settings up on my ipod to balance the sound.

Features:
1.) Sennheiser- nice cord, push to talk button (temporarily mutes NC and sound which is great for interruptions on airplanes).
2.) Bose/Audio Technica- just the basics. Bose simply an on/off switch.

Price:
1.) Audio Technica- $150 to $225 depending on how you shop.
2.) Sennheiser- $200 to $275
3.) Bose- Hard to find below $300+.

Noise Cancelation:
1.) Bose- No question here, far surpassed the other two. Best Noise Cancelation.
2.) Audio-Technica- Good Noise Cancelation.
3.) Sennheiser- Not sure what happened here. Incredible sound, satisfactory noise cancelation.
Summary:

I ultimately kept the Bose because I was only using these for flying and the Sennheiser's (as much as I loved them) let me down in the Noise Cancelation department. The Sennheiser's had by far the most superior sound, but the Bose Noise Cancelation was night and day. The Bose are made very poorly for a $300+ product, it was disappointing.

Final assessment:

Audio-Technica- best balance of value for money
Sennheiser-Best sound and comfort
Bose- Best Noise Cancelation
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Amazing sound quality. Good noise cancelling. high range of frequencies.. Just heard something that I've never heard before in a song, which made me write this review. Feel the power of "made in Germany" !
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Having tried the Sony noise canceling earphones many times I initially was tempted to purchase what I thought was top of the line for noise reduction earphones. The number of reviews I read favoring the Sennheisers PXC 450 strongly influences my decision to buy them as I was not willing to give up quality over bass response and I've not been sorry.