The A20 (I have one) is truly a lot better than the old Bose X (of which I have three).
And the Bose X is at the very top of the headset market - equalled only by the Lightspeed Zulu, and possibly one David Clarke headset which is OK if you like your head to be like
this (due to the vice-like pressure) after a few flights
If you plan to fly long-term then buy a Bose.