Unlike a window, a peephole is not intended for contemplating the view which it frames, nor the light gently falling within the interior of the space it opens.
Even when closed a window opens, whereas even when open a peephole maintains the integrity of a closed space.
A peephole provides security of the interior, a window comfort of the exterior.
A window reveals. A peephole conceals.
A window allows for various perspectives and varying viewing distances. A peephole only one, and that distorted.
A peephole is a puncture, a window an embrace.
The nature of a peephole (to be peered through from up close with a single eye) renders one half-blind. A window, on the other hand, encourages one to look with both eyes open wide.
One looks through a peephole with eyes of fear. One looks through a window with eyes of wonder.