DC is a market leader and has been for years. You dont get there by selling crap!!!!!!!!
DC are not crap but they are very uncomfortable, which is not significant (for most people) on a quick training flight (or a quick flight of any sort) but does one's head in on longer flights. And all £200 headsets have poor noise attenuation.
DC are selling because they have always been selling. They are a kind-of Harley-Davidson of the headset market - stick an American flag on it and a certain % of punters will always buy it. They are also solidly built which is an asset if people are going to kick them around, which, I suppose, is important if flying e.g. a single door plane in which the headsets get left on the seats and as people climb in (stepping on the seats) they step on the headsets.
The point is that things have moved on since the 1960s when DC were state of the art. The best of today is Bose X and the Lightspeed Zulu. DC have nothing that even approaches these in performance.
BTW, beware of bogus advertising which has been common on headsets since I started flying in 2000. The attenuation figures are often made up on the spot. In was at a well known pilot shop last week and looking at some of the quoted "total noise reduction" db figures it was obvious they were nonsense. Never buy a headset on the advertised db noise reduction. Bose don't even give this figure...