Bose X
As most people in this discussion, I am very happy with the accoustical performance of the X's after 5 years of use in R44.
Reliability is however not so good. I had problems with ear-cushions of all of them, one had a broken support and all of them had broken plugs.
Bose does not allow you to fix that, so you end up with repairs that are close to the new price of a lesser model, so 'cost of ownership' is very high.
Delta3