I'm not claiming it's about per chip hash rate, and claiming that there are a few factors which need to be considered, not just power efficiency.
You're right; time to market is pretty darn important too.
oops.
You need to consider the hash rate, the power efficiency, the cost and the volume of the miner too.
Volume as in density, is mostly a non issue outside of collocation, which is a dead end anyway. Take a look at the largest mine. notice the shelve spacing here:
http://www.thecoinsman.com/wp-content/uploads/2014/08/40-1X33zo7.jpgor the rack spacing here:
http://www.thecoinsman.com/wp-content/uploads/2014/08/39-GQF0zFa.jpgThey could easily cram 3 or 4x as many rigs in that warehouse, if it werent for power/cooling limitations.
As for "hashrate", its not a metric, its a variable that you can scale arbitrarily. What matters is hashrate/watt and hashrate/$ on a system level, but the latter is also highly dependent on power efficiency per chip, since much of the overall cost is in power delivery rather than the asics themselves.
