I think there are two key factors to consider when comparing mining systems/chips.  1) system dollars per GH.  This is where big hot chips like Hashfast run into trouble.  The cost (expensive board, big power supply, water cooling) makes scaling a mine too expensive.  2) system power (at the wall) per GH is also a factor as we all pay for power.  The lowest I have heard HF do is about 0.90w/GH at a low hashrate 320 GH/s.  There are lots of small chip systems that beat the crap out of this system power per GH.  So small chips is the way to go for both cost and power.