Another view
I have the dissenting view here: Saying that one brand or model of headset is more comfortable than another is like saying that you should wear a particular kind of shoe, underwear, or whatever. IOW, what's comfortable for me might be unbearably painful for you. And vice versa. And even if the item is top quality and well made -- like a David Clark headset.
I've been flying for 20 years, and I have never, EVER been able to get comfortable with ANY DC headset. Not even the 13.4s with the soft headband and ear cushions. I'm sorry, but I just can't stand Clarks, no matter how well built they are or how good their service is. I just think they're overrated because of some kind of herd mentality. Also, I've found that their audio quality isn't that good when used with other kinds of headsets on the same intercom.
I've used the Lightspeed 20K for over 2 years now and it is superb. Audio quality, both transmitting and receiving, is as good as or better than any Clark, Telex or Bose I've ever used. I can actually forget I'm wearing them, and I've never been able to say that about any other over-the-ear headset.
Final suggestion: Try before you buy, and make sure that you can return it after a reasonable trial period (in good condition with all packaging, of course).
Good luck!