One story house vs 2 story house temperature.

It is (largely) a matter of comparative R values in the building component, as well as comparative amount of sun that gets on similar components.
Given equal attic insulation and equal attic venting, the upstairs would logically be a touch warmer since the additional wall area gains heat and therefore rises.

The reality is that give equal values, the two story house is a much more efficient use of energy and materials for a variety of reasons. Do a search on this site, as there is a rather lengthy thread on that subject.

Icarus

 

I agree with this opinion. My 2-story house was much hotter upstairs than down and with the typical tract housing A/C system it was difficult to control temperatures and was very inefficient.

That being said, there are cases where a 2-story house could be MUCH more efficient than a single story house but since your question seemed to assume all parameters were equal then I still agree with the above post.

 

Anecdotal, but my neighbor's home is about the same square footage as mine. His is a traditional two-story, mine a one-story ranch. Both are built to the same code. He keeps his home both cooler and warmer than I do. Mine is much cheaper to heat and cool, about 20% less, but I've taken some small extra steps to improve insulation inside and out and have a trick thermostat that saved about 5% energy use comparing year-over-year consumption.

 

You prove the point of conservation. Regardless of "codes" the net effect of "some small steps" is dramatic. 20% reduction in use of energy is nothing to sneeze at. Even two side by side houses that are in reality built exactly the same, a considerable savings in heating and cooling can be had by doing thing as simple as adding a sweater, closing the shades at night, and OPENING them to the sun during the day during the heating season!

Cooling, same way. Keeping the house closed during the heat of the day, opening it at night, planting shade trees, turning the t-stat up a notch or two. It used to drive me nuts visiting my inlaws in FLA. I was constantly freezing their house, my father in law would wear a sweater in the house! But would they turn the AC up a notch??? No.

Icarus