I will take a crack at trying to explain.

For industrial power users they generally need three phase and it’s benefits for motors which are far simpler in design and more efficient than single phase motors. By adding the third wire there is also a good bump in available load rating without having to upsize the wire and panels feeding everything. Get three phase if you are going to have big HVAC or big ventilation fans.

150kW on single phase is around the 625A per leg range which needs some serious wire and larger gear.

150kW on three phase is closer to 425A per leg. This makes for smaller wire sizes and easier installations.

Like NotFuzzyWarm said, the line provider will do their best to balance loads as they connect services. Sure your load might tip the scales a little but in the grand scheme when a power plant puts out 400MW (1000 times the size you plan to be) your load won’t be perceived as unbalanced by the generator.

In an ideal world a mine should get 240/415V three phase but that is tough because that is a non-standard system voltage in North America.

Do the power supplies run more efficient at higher voltages? I do not believe so, at least not enough for it to really matter. Rectifiers and electronics are really efficient these days. What is nicer about 240V over 208V or 120V is that the breakers, plugs and wires to the miners can be smaller which is generally cheaper. Plus there is less chance of fire if someone accidentally brings a 18awg IEC cable into the facility. At 120V those will burn up right quick. At full 240V there is much less chance of running an individual circuit over its rated max, at least accidentally.

But profit is king. Do what is available fastest and most cost effective. You want to be running, not messing around with electrical services.