I think the point is that nothing from Arm will come close in performance. Tri-gate is the game changer.
Try to do anything beyond web browsing or watching a video and you will lag using Arm. The reason Arm cores are so power efficient is that they have a lot less transistors.
low transistor count + lesser instruction set = more cpu cycles per calculation
The reason Tri-gate gives Intel a tremendous edge is that it reduces power draw required per transistor by 10x when idle, and reduces active power by 50% with the same performance.
The 10x power reduction when idle benefit is very important since leakage has always been an issue for Atom, for instance an Atom powered phone would have run out of juice just sitting in your pocket, probably why you haven't seen any Atom powered phones, yet.
I see you've been doing some reading.
You've come to the conclusion that tri-gate is a game changer regarding ARM V Atom. We have to agree to disagree on that one. You'll find the Intel camp agreeing with you and everyone else agreeing with me.
ARM (Cortex A9) outperforms Atom (even at a lower clock in some cases) today. We don't know enough about the 32nm Atom to know if it has any major rework (at least I haven't seen anything?) - if it hasn't then ARM will 100% retain the performance, power consumption and price advantage until the 20nm Atom arrives in 2013. At that point, you say Atom will win, from what I've read, I say no. Again, we'll have to agree to disagree.
Yes, ARM have less transistors which is one of the reasons why they consume less power - but not the only reason. The lesser instruction set comment is bait no?:)
The idle issue you mentioned is valid and tri-gate will help Intel in this regard. You can also reduce leakage by good design... ARM has a whole set of design techniques it uses to reduce power (have a look at clock gating as one example).
When designing for low power you have to start from the ground up and until Intel do that they can't be in the game.