I have never tried the QC-15's but own the QC-3's. They are very effective at cancelling ambient noise. I love them on the airplane. The audio quality is excellent. There are a couple of issues with the -3's. They have a proprietary rechargeable battery. If that battery should die, the headphones won't work. I have never had this happen but it is a possibility. The battery will last for hours. Not sure how many but I've used them for 8ish hours with no problem. Secondly, I find that they make the hard cartilage part of my ear sore after using them for 3ish hours. I don't use them on a daily basis and like anything, maybe my ear would get used to it if I used them more. I have owned these for about 5 years now and love them otherwise. Hope this helps.