ARM vs x86, RT vs 8 vs iOS vs OSX - who wins?

Just a quick thought, but what it's really going to come down to is computing power and battery life. The iPad is an excellent device, but lacks the power of a proper x86 chip to run certain applications. x86 chips are powerful enough to do anything, even in smaller form factors like ultrabooks, but they aren't where they need to be in battery life. So, it comes down to this: Will Intel/AMD be able to solve power issues first, or will ARM manufacturers be able to scale up the technology quick enough to run any application? It could honestly go either way right now. ARM chips are getting a lot more powerful and Intel is starting to put out some excitingly efficient stuff, and AMD's APUs bring a surprising amount of power in an affordable and slim package. What do you guys think? Will the slimmer OS always win out, or is there room for the more powerful systems to hold their own?