Actually, Intel is moving Atom to 14nm (!) in 2014: http://www.geek.com/articles/chips/intel-14nm-atom-chip-in-2...

ARM chips are only (notably) more efficient when they slower. If you compare like vs like it's not as simple. Eg, 2 GHz ARM A9's are roughly more as powerful as a 1.8 GHz Atom, and have similar power budgets (leaving aside Intel's pathetic chipset & graphics support for now)