Obviously, smooth coat Border Collies have an advantage in hot weather. Ask any Border Collie owner in Texas or any lion in Zaire. Less of a coat is better but too little is a problem. If you have your choice and you want to work long hot hours, you get a smooth coat Border Collie. The answer lies in how the coats develop in the two kinds.
Smooth coats have much denser fur, like a giraffe or wildebeest.
If you shave them, you end up with a short-haired, low hair density dog. This isn't what you want as the heat gained will outdo any heat loss. What you want to do with a rough coat is to get rid of the undercoat, with an undercoat rake or brush. You want to make your dog out like an Arabic Border Collie. Loose fitting fur that completely covers the skin.