Preventing break-ins isn't the point of security cameras. Their purpose is reacting to break-ins. Maybe you can give the police a picture of the burglar's face. Or their license plate or car make/model/color. You can see what they took, so you don't leave something off your insurance claim because you hadn't yet noticed it was missing. Your dog can't do any of these things, and a camera is a much smaller commitment than a pet.