150kw is getting into 3-phase territory but still very practical for single phase service. It comes down to cost of the panel (size and amount of copper in it) and if the power company needs to supply you with a different service transformer to feed the building. As Mikey said, go with what is cheaper.
I am scaling up to around 400kW and actually still on the phase conundrum, so now I'm asking why 150kW was "getting into 3-phase territory" and so this implies I should be getting 3-phase for 400kW facility?