Should you buy A bunch of cheap GPUs and have them all mining the most profitable coin or have 1 or 2 expensive GPUs mining the most profitable coin
There is a good way to work this out mathematically. What you need to find out via a little searching is the *efficiency* rating for the particular GPU mining that particular coin. Efficiency is a measure of how much electricity a GPU uses for its hashrate. The lower the efficiency number, the more hashes you’ll get for your electricity consumption. With this concept in mind, it becomes a lot easier to compare miners and their prices.
For example: an Antiminer S7 has an efficiency rating of 0.25 W/Gh, and an S9 has an efficiency rating of 0.1 W/Gh. The newer S9 model is therefore 2.5 times more efficient! Although it costs about 4x more, the S9 will save a lot of electricity over time, meaning that it’s a better buy over the longterm than 4x S7s.
Tip: the Radeon RX 480 is one of the most efficient cards around.