First method costs you 10000 kWh energy and gives you 99.99% clear water.
Second method costs you only 1 kWh and gives you 99.00% (safe for drinking)
Which method is preferable?
Second method costs you only 1 kWh and gives you 99.00% (safe for drinking)
Which method is preferable?
That is easy, the first. But that is a straw-man argument.
If the decision is: costs 1.001 kWh and gives 99.99, versus 1kWh and gives 99%, I might decide the extra purity is worth it.
The "centralized is more efficient" might be theoretically true, but in practice the difference might be so slight it doesn't matter.
Theoretically, it would be more efficient if all of our computing happened in huge data centers located near cheap hydroelectric power.
Practically, though, only some of our computing happens that way (e.g. searching terabytes of data), because it is more convenient for us to carry around powerful little computers and we value that convenience.