They're both peer-to-peer car-sharing services, because the two things that really work for car-sharing is, one, the car has to be available, and two, it's within one or two blocks of where you stand.
Ambas ofrecen servicios cara-a-cara para compartir coches. en donde dos aspectos son fundamentales: uno, el coche tiene que estar disponible, y dos: debe estar cerca, a unas pocas cuadras de tu lugar de partida.