After reading posts on this site for several months, amazingly this is the thread that prompted me to post.
I prefer to run in men's basketball shorts. This is 100% for functional reasons. They are long enough that they don't ride up. The band is heavy enough that my iPod stays in place and the material is such that it doesn't chafe. With regards to the heat, I haven't noticed that shorts really make a big difference when its over 80 degrees out. I stick with the dri-fit type shirts and keep well hydrated and that seems to be enough.
Great discussion though. I've always wondered the rationale behind short shorts.