I find the QC3s a lot more comfortable than the A20s. The QC3s are both lighter and have a more comfortable headband -- I don't like how the A20s sit/press on the top of my head. The A20s are designed to deal with the noise you find in a piston aircraft. Flying the major airlines, you're not going to be dealing with that kind of noise, so the QC3s are probably both completely adequate and easier to carry.

I've flown with my Telex Stratus 50Ds and they were total overkill. Very quiet, but far more than was needed. And there was that matter of strange looks.