I don't see how you can compare energy efficiency between something powered by electricity and something powered by natural gas. They're two entirely different

I don't see how you can compare energy efficiency between something powered by electricity and something powered by natural gas. They're two entirely different energy sources. The electric one doesn't involve putting more CO2 into the atmosphere, at least directly. And cost is completely variable, as electric and gas prices both vary wildly depending on location and time (gas became much more expensive in the last year).