X11s not very good for the same reasons as the Bose; poor passive attenuation so high frequencies get through. I bought a set when they came out and sent them back within 2 weeks. The other problem with the X11s was the quality of R/T reception; while other ANR headsets clean it up the X11s actually reduced the clarity and it was like listening through a cardboard tube. While these headsets claim 'full spectrum noise reduction' if you look at the graphs the amount of attenuation at higher frequencies is minimal, so you need decent passive attenuation at these frequencies if, like me, you want to reduce wind noise (hissing not farting). I have not found anything yet to beat the Sennheiser HMEC 400/450 in this respect although they have more clamping force than the Bose or X11s. New model HMEC 460 might be worth a look but not cheap at £600 or so.
TRY BEFORE YOU BUY or at least make sure you can send them back if you don't like them.