The 2k12 feels a tad heavier, stable, and more durable than the Vapor. However, the cuff/topline ( go to this link if my terminology is confusing: http://www.independentsole.com/stora...=1315971830226
) ripped at the top after about two months. But I was glad they lasted that long, in fact they lasted over half a year if I recall correctly. The Vapor 9's on the other hand offered me more quickness due to their lighter weight, and it also had better traction, ventilation, and of course nice aesthetics. The durability wasn't quite up to par as the 2k12, but at least the cuff didn't wear out at all. Come to think of it, the Vapors had pretty much equal stability just less durability. Honestly, I much preferred the Vapors because of their quickness and because I live in Arizona where I need highly ventilated shoes.
I also forgot to mention, the 2k12's, once broken in, became very roomy and my toes sometimes hurt because of that. The Vapors fit like a glove for my medium-width feet. Happy holidays!