With an escort you get a comfortable environment, a clean room, perhaps a shower, a girlfriend experience, and a modicum of safety. the girl might see one or two guys a day in a non-rushed environment.
A street walker gives you 15 minutes in a car, probably did 10 guys in the last 5 hours, smells of crack ( or the other way around!), constant danger of being busted by law enforcement, and your neighbors might drive by and see your car stopped at the side of the road (the privacy element).