I'm a newbie too, and I fly both (headsets).
The FTO has A20s. They work really great, as they should, at +1k € a pop.
Today I was refreshing emergency skills with a FI and enjoyed their A20.
Privately I got me a DC H10-66XL
https://www.davidclark.com/HeadsetPgs/h10-66xl.htm
They cost exactly half of what Bose is asking for their A20 and they weight exactly twice as much.
But they kind of are twice the value because I can switch Microphone impedance between S-300C and BO105.
Furthermore, should you end up with an empty battery (ANC battery that is), as I did a fortnight ago the DCs are passively attenuating much better than an A20 would, so the grapewine hisses.
However the mic beam of the DC is a tad shorter than the one of the A20.
My personal reasoning went along the line of
A20 + second "cable" for the other impedance is way too much money when I can get a versatile, albeit heavy 66XL.
If I'd only fly the 300C I might have reached for the A20.
P.