HUGE differences. First, to legalize something you have to have a new law about it. In places where prostitution is legal, there are so many laws surrounding it. The license is just one. Ask anyone who has worked at a NV ranch. There are so many regulations surrounding it that it makes it unappealing to most people- hence the larger illegal part of the business in the bigger cities where it isn't legal. There are laws about medical testing, where the workers can be and during what hours, and lots of other stuff.