I have a set of the HMEC 25's and they are tragic in a light aircraft. They do not cut any of the background noise out as they have zero passive attenuation. Because they are subject to the high noise of a non pressurised aircraft the battery life is alos tragic.
I use the Bose-X for private and work flying and they have proven to me priceless in terms of performance. They have suffered a very hard life over the years and I have finally managed to get the cabled that connects to the LHS ear cup to develop a break which gives an intermittent failure of the ANR. So off to HS at Shoreham for repair. I have been lent a set of the lightspeeds while the Bose are away for repair and can say I am quite impressed. The ANR is not bad at all, certainly in the Bose league and the Bluetooth is a very cool function. I have my iPhone connected to it and it BT streams music and the phone nicely. They are heavier than the Bose and a slightly more bulky but not show stoppingly so.
It would be a hard choice for me to choose between them. I think only brand loyalty would take the edge on the Bose for me if I was buying again.