Just based on efficiency, the general trend of what you've just said is correct. The only additional parameter I would include would be weight.
What weight are you carrying? What are you trying to move? If you're trying to move a fairly large vehicle—think of garbage pickup in the urban environment—you may find that you don't have an efficient overall capacity using an electricity-driven truck. Hence, you might want to use natural gas, just because of labour time and the efficiency of the actual function you're trying to put together.
If you did a truck-for-truck comparison, it might be more efficient, but if you look at the function, it might not be, because of the weight you're carrying. Therein lies the rationale for why we looked at the two basic functions of return-to-base vehicles for natural gas in the medium- and heavy-duty area and then the long-haul heavy-duty vehicles.
Largely, as the technology advances for infrastructure, carrying heavy weight, and range, the switch to electric may come. It's hard to predict when electric vehicles might be capable of doing those heavier-weight but local jobs. As I said, I think natural gas is a legitimate transformation now from gasoline or diesel, but it is interim in terms of moving to a longer-term solution.
