[Espeefan]

I'm going to make a bit a blanket statement here, but generally speaking most brushless speed controllers, cannot run a brushed motor, however there are some exceptions to that rule. Electronic speed controllers offered by Tekin, Castle Creations, and some of Novak's older ESCs are able to run either brushed or brushless motors. You just have to be sure that the one you buy can run either, if that is really what you want.

If you never plan to run a brushless motor, then there is no benefit to buying an electronic speed controller that can do either.

Speed controllers that are for brushed motors cannot run a brushless motor at all. They do not have the circuitry required. I would take a guess and say less then a quarter of the brushless speed controllers offered today are able to run brushed motors. Normally people do not mix and match brushless speed controllers with brushed motors. It's usually a brushless motor that people run with a brushless speed controller.