I began to learn to fly helicopters using Bose X. So good that I fitted them (5 sets) in each of 2 EC120s and an R44 (4 sets). Good cheap deals on e-bay so a fraction of the cost of A20. Spare parts easy to come by. No Bluetooth, but then I don't want to take telephone calls or be distracted by music when I am flying.
I found the ANR sets much lighter on my head, and on long trips after 4 or more hours continuous use that really makes a difference.