PaulSA
I was in a similar situation to you earlier in the year, being unable to make my mind up between Bose and David Clarke. Fortunately I was in the States at the time, where most headsets are significantly cheaper than they are in South Africa (the exception being the Bose which were only marginally cheaper). I wasn't able to reliably compare headsets whilst there so in the end I bought both a Bose X and the David Clark H10-13HX set on the grounds that I could sell whichever one I decided not to keep when I got back. I still haven't done that though (despite the amount of flak I receive for having two headsets!
I find myself choosing the Bose over the DCs when I fly. They are lighter, with less clamping force and are consequently more comfortable than the DCs. I also find that voices tend to be clearer using the Bose, including my own (which may indicate a better mic but it could just be the headphones). That said, I still find they occasionally make a popping/clicking sound every now and then which I think might be related to a change in the airflow over the exterior of the earcups around the "TriPort headset openings".
The DCs are a solid piece of kit and I am not nearly as circumspect handling them as I am with the Bose, regardless of their difference in price. I suppose I worry that the Bose might break (and treat them accordingly) while the DCs will always work - probably why I haven't got around to selling them yet, they're my backup!
In adding to what Outwest and others have said: If you want the best, get the Bose, if you want them to last forever, get the David Clark.
The DC X11s had just been released when I was in the States and weren't available with a helicopter plug. I believe this is still the case, although I think they'll release one sometime next year. Very neat headset with lots of features, it looks like DC's response to the Bose with far less passive reduction and a lot more active reduction. I see from your profile that you fly fixed wing too: you might consider buying them along with a converter for helicopters. I actually ended up doing the reverse - buying helicopter headsets, and a fixed wing converter. It keeps the helicopter cabin a little bit neater at the expense of the stereo capability of the headsets (I don't actually fly fixed wing but have a friend whom I fly with who does).
Well, I have rambled on for quite a bit now, hoped I've helped. If not, you're welcome to come compare them yourself if you want. I fly out of FAGC - send me a PM if you're interested.
Cheers
Turbinefan