It's not just about power efficiency.
In so far its not yet the case today, it will be next year. Power consumption will be by far the most important factor. Not only directly as opex, but its also driving PCB and system costs. Asics themselves are cheap; DC voltage regulation, cooling etc are comparatively quite expensive and those costs scale with power (in)efficiency.
Sure, competitors may have better power efficiency but what hash rate will those chips have? Look at Bitfury or Spondoolies 40nm ASICs and compare them to AMs gen 3. If those chips were overclocked to match the hash rate of AMs, what would happen to their power efficiency?
Per chip hashrate is meaningless. Particularly if you dont take in to account die size. Even if you do, it only affects silicon cost which is probably among the least important factors.
Here's what FC said on the issue:
So he says he doesnt know yet.
I'm not claiming it's about per chip hash rate, I'm claiming that there are a few factors which need to be considered, not just power efficiency. You need to consider the hash rate, the power efficiency, the cost and the volume of the miner too.