Have been using a Bose X for the past year and have no complaints. Really comfy even after 6 hours flying.
Never used a DC but one of the guys I fly with has one and raves about it. The only down side I can see with the DC is that my friend was changing his battery (square 9V) every 20-25 hours where I am getting 70-90 hours out 2 AA's on the Bose X.
Down side on the bose is that to change from Hi to Low impedence machines ie going from S76C+ to A++ requires you to change the Mic which entails buying the whole mic/lead/battery pack which is pretty expensive. I currently use a Peltor in the A++ as I dont fly that much in it but would invest in the extra lead if I did more.
Hope this helps.
PS if you go for the Bose buy in the US as they are a lot cheaper than UK.
Cheers
L'