My main intention when I started responding was to point out the much larger winter heating differential in the north, in response to the discussion about heating versus cooling costs and efficiency. I am not sure why I got distracted about Miami versus Phoenix and inserted that before posting.
My experience living for a few years in a tropical country was that locals acclimate and do not cool nor dehumidify their living spaces nearly as much as many Americans seem to do. Much like in Florida, you will see people running around in jackets or even knit hats on slightly cooler days when someone from a colder climate would already think it is warm and time for shorts.
I think it is difficult to compare different regions with different climates and cultures. It seems impossible to me to choose a metric that isn't inherently biasing the analysis towards one arbitrary normative standard. Compare similar regions or one region year-to-year to evaluate the efficiency of local practices.
Edit: another issue is the daily cycle. You can use thermal mass to smooth out daily temperature extremes but that doesn't work when you spend weeks or months with temperature differentials that remain offset from comfortable.