Night sights are almost ALWAYS a good idea on a defensive handgun. It doesn't have to be totally dark, to be too dark to see the outline of your plain sights against the target. Think about being in a darkened room, with a potential target moving toward you from a partially-lit room. You I.D. the target, then as it moves toward you, it turns into a silhouette as it enters the hallway/room entrance. Those little glowing dots will be mighty comforting under those conditions.
They are also very useful for locating your handgun on/in the nightstand when you are first awakened by that Bump/Crash in the dark, dark night.
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)