As a rule of thumb:

Passenger cars with 30+ mpg are less polluting than equivalent EVs powered by coal per mile driven (not including manufacturing). Cars with 45+ mpg less polluting than EVs powered by natural gas.

This formulation lets you look at your own car and grid makeup and see that, for most people, the EV even when better is marginally so.

"Efficiency" is a red herring because you can't compare like for like. 40% efficiency of a Prius includes generation and use, but 90% efficiency of an EV is only the use not the generation. For example, an EV powered by solar is often <20% efficient since the panels are only around 20% efficient, which is why they never talk about that. How much energy costs per mile, how much pollution - this is what matters.