The Bose X are excellent but if you are in a noisy light a/c you will find them next to useless if the power unit fails as in passive mode you cant hear a thing!
When I did my research I ended up with the Bose headset for two reasons, 1. comfort, 2. The X11 DC was the nearest rival and I heard from quite a few flying instructors who bought them that they were good but unreliable.