With either solid or plantation shutters, you can close them at night and provide privacy from the outside world. They are also a deterrent for an outside intruder as they provide another layer that would be needed to break through. During the day, shutters can be opened to provide the warm of the sun and provide needed natural light.
Because you can adjust the position of plantation shutters, you have the best of all worlds. When you need the light, simply adjust the louvers accordingly. This will allow the light to stream into your home while still blocking the view of an outside intruder.