[citation][nom]bystander[/nom]I don't know if you are aware, but Win 8 is being developed on ARM as well. It won't be released this year, which is why the initial Win 8 devices are x86, but if you look at the new Atom benchmarks and power draw, they are doing very well in those departments now.[/citation]
The big problem is the level of control. Apple has control from beginning to end, and can create a synergy between hardware and software that Dell can't. Dell doesn't have an ARM license, so has to use someone else's chip. Apple can develop their own if they wish. Apple can match their OS to their hardware very specifically, not create a bloated OS that needs to interface fairly effectively with different pieces of hardware that other vendors might have.
I'm not convinced W8 on ARM is going to be popular, or if it's a good thing if it is. It will create confusion because you'll need two different versions of an app, and that's not a good thing.
x86 is inherently inferior. It adds overhead that ARM does not have, and while it may have some times when it is competitive, overall it's the wrong instruction set. For everything. Intel's manufacturing surely helps a lot though, and for desktops it's worked because power isn't as important and penalty manageable, but for mobile devices, the penalty is greater.