depends on what you mean by turnover as a 20 pack can be broken down and sold faster for 20x small profit faster than 1 unit. If you are taking in to consideration mining/power cost in to consideration, the 20 pack still wins as you can mine with it as a group of 20, 19, 12... until you are down to the last 1 and probably still have the PS/connectors to sell off while still mining.
If I had 1Th/sec SHA256d miner, i'd be mining and not thinking of selling it ever.
That is my view on it. Other opinions will vary, contents may contain nuts, strawberries, cucumbers, PCBs, Lead, tobacco, mercury, and other possible toxins.