Bose X vs Zulu
I own both the Bose X and the Zulu (1), and have about 50 hours with the Bose A20. 95% of the time with the X and the Zulu is in King Air 200. I find both the X and the A20 to be less comfortable than the Zulu: I get a hotspot on the top of my head with both. Nothing at all like that with the Zulu, they are fantastic. My Zulu is four (maybe five?) years old, probably 1000 hours, and no problems other than an earseal coming apart. The Bose has had an electronics repair (cant remember what the problem was), as well as a cracked earcup stirrup (the forked part which connects the cup to the headband). In my opinion, the Bose's look as if they are better quality, but they are not.
Personally, I cannot tell the difference in noise reduction between the three. Maybe the A20 is better than the X. I find the Lightspeed much more comfortable, and the music streaming is a must-have for me. I havent checked the passive reduction, but the Lightspeed is pretty terrible with no battery power. I always cary spares and batteries are easy to change in flight. I have also never had any functional problems with the ANR, so the passive has never been an issue. Apparently the passive is better with the Zulu.2, and I have just bought one (currently on an $800 special), and am selling my Bose.