Pros: Operates on batteries, adjustable light sensor
I have 2 inside mount doorkeepers with the light sensor and have had them for over 3 years. They have never failed, and I routinely change the batteries once a year - just to make sure they don't run out. It closes so slowly, so you don't have to worry about a chicken getting caught in the door while it's closing.
This doorkeeper is worth every penny! I never have to worry about my chickens not being closed up at night.