Originally Posted by G31
That is not possible to answer in every circumstance. Can you see an AR15 outline? Most likely from any distance. A pistol or revolver? Maybe across the room in your house, or 15 feet away outside. A bat or crowbar has a unique shape, and a gun is held in a unique way (most knives, etc. don't have handles at the rear, giving it a gun-like profile in a hand). Can you tell if a tall, skinny man is in your house under dim light? How about a 260 lb fat guy that doesn't belong? Of course.
Along the lines of what has been said, night sights are guaranteed not to be a gimmick, nor a waste of money. There is no physical way a person with the ability to see cannot benefit from them, whether they think so or not. It's part of the nature of sight. Whether its worth it to you is a different story, and I respect that.
The fact that it is not possible to say in every circumstance is the point I guess. All it takes is one unjustified shooting to ruin your life. Given the choice between a light and night sights both seem a good choice. Just a light seems a good choice. Just night sights seem to be an irresponsible choice.