What I've heard with regard to the diffferences between the two versions, from doing a lot of research before acquiring mine:

• Fidelity is slightly better with the QC1s
• There's a slight but noticeable hiss with the QC1s
• Noise cancellation is virtually identical in both
• Battery life and appetite is dramatically improved with the QC2s

I rarely use my QC2s when I'm not flying, but I fly every week. I seriously doubt the difference fidelity or hiss would be noticeable in the air with a circumaural headphone like the QC series.