True, and it was AMD that broke the 1GHZ barrier while intel tagged along - but even if later they always managed so far to come up with the superior technology (however power was not as constraining as it is now).

I can't really say If 1ghz ARM = 1ghz X86 since we have no objective testing methods.

But what I'm sure of is that ARM will never best the "i" series and if they'll ever do, there's already gonna be i2.

Regarding power management, I think it's CPUs that should adapt and not energy sources. You always have to think extreme and extreme means doing a lot with little power.