cheaper but it has the possibilities that the car has been over used as a demo car. Some kids just like to test drive the cars pretty hard. Unless, you are buying an expensive car which a normal kid doesn't have a chance to play with.
I was shopping for a car recently. I was very hard on the demo cars, pushing the car to its extreme limits to check things out.
I'm not a kid But I would like to see performance on the car, that's why I try out the car in a hard way. That's also why I would never buy a demo car. The first 1000 KM is very important for any car. You have to be very gentle to a new car. But to test drive, you cannot be too polite not to try everything out, right?