Run-flat vs regular tires - milages and performance

The run-flat tires that came with my car when I purchased it will soon need replaced and I am wondering whether I should replace them with another set of run-flats or get equivalent standard tires. I would like to hear comments whether the stiffer run flat tires offer better milage and performance (for street driving)compared to standard top quality regular (all weather)tires?

For the sake of this discussion,ignore the need for a real spare tire, and assume the tires will be the same physical size(diameter). I don’t know for sure, bit I assume that run-flat tires are heavier and add more unsprung weight, however I am not concerned about ride comfort between the two types of tires, just gas milage, performance, safety, etc.

For practical purposes, there is no difference between RunFlats and non-RunFlat tires - except to say that RinFlat tires will hrd somewhat harsher.

However, you will hear a lot of opinions to the contrary. Many of these are based on comparing higher speed rated Original Equipment tires to lower speed rated replacement market tires. Typically the former do not wear as well as the latter, but that is typical for the difference between the 2 groups, rather than the difference between RunFlats and nonm-runFlats.

I would tend to agree. While there are some general differences, they just are not enough to worry about.