I'd take the 6P. First, after three straight HTC devices (Incredible, Rezound, and One (m8)), I'd like to try a straight shot of Android. I'd take the 6P over the 5X because I have a thing for multiples and powers of 3, and 5 is neither a power nor a multiple of 3.
I admit I'd also like the bundle of AndroidCentral goodies. That seems cool.