[sashua]

I don't have access to listen to either of these but if I were to buy one on a wag, is either a clear choice over the other?
 
I am also open to other suggestions here. I just need a great pair of folding headphones (small form factor) that sound amazing. Price is of no concern here but I do a lot of travelling.
 
I usually listen to a pair of Audeze LCD-X's and I know I won't get that kind of majesty in a portable set of phones....but I want as close as I can get in a small, travel sized, on or over-ear set....and I'm willing to pay for it.

 

[halfinfinity]

KEF M500's. 
 
The quality is definitely superior to the B&W's. Just by the way, the P5's don't fold. Only catch is they don't have the greatest noise isolation.