The OEM camera is blatantly obvious. It is a big, black square looking thing attached to the top corner of the license plate. It is more expensive as well, but the advantage is that you see the rear bumper and ground immediately behind you. You may not notice a car parked a short distance behind you.

With an aftermarket camera in the roundel, it's hardly noticeable. Plus you get more of a wide angle view behind you. You can easily see what's directly behind the vehicle but you don't see the bumper. This is where my park distance allows me to judge the distance.