I finally feel qualified to say something about the K2 Cortex, though this is still kinda early.
All comparisons are to an Atomic Hawk Ultra 130 RS, and only make sense given the context of MY foot and the fact that I'm using a zipfit liner, but there's nothing groundbreaking given what
@tomPietrowski has already shared in here.
Bootboard is nice and absorbs impacts. Boot plastic is dope, though kinda temp sensitive, and has nice heft and power. Upper BOA is awesome in what it does with fit and flex. The boot is not harder to get in or out of when warm... but kind of a pain in the ass when cold.
Fit:
Tighter heel, but also more of a heel cup.
Lower instep.
More squared off in the toe, which has a tad more room both in width and height.
Upper cuff fit with the BOA is insane.
Takeaways:
Upper BOA is more of a gamechanger than lower BOA.
If there was a boot that had the midfoot forward of a Hawk Ultra 130 RS and the midfoot back of a Cortex, plus upper cuff BOA, it'd be the perfect boot for me.
I'll be skiing park pretty aggressively (i.e. aggressively mid) tomorrow, which I have yet to do in these boots. Also has not snowed in weeks, so haven't skied them in fresh snow/wider skis.