Why would anyone recommend 3 phase over a single phase for mining? it really makes no difference, since you are going to be using nothing but PSUs that need only a single phase.

Remember that by the end of the day you will be using 3*single phase which is just like running 3 separate single-phase wires, what you should focus on are only the total allowance and the cost.

You tell your electric guy that you need for example 100kw at 220v in the cheapest form possible, I don't know about the cost in your country but I'd say a single-phase set-up would be cheaper.

I have 3 phase but only because I really don't have any other option, the nearest supply I have is 3 phase 11KV, so I have an 11KV to 380V (3 phase) transformer (the only type of transformers available here), it does come in handy sometimes, for example, I was able to get some 3 phase exhaust fans ( certainly a lot more robust than a single-phase fans) but I then have to worry about load balancing and shit, so with everything else equal, a single-phase will be it for me.