The night sights are a passive, non electronic tool that will allow you to target a silhouetted intruder, in near total darkness. They also function as ordinary sights in brighter, ambient light.
The weapon light is an active, possibly aggressive tool that will allow you to ID, momentarily blind/confuse, and possibly pin-down an intruder. Consider skipping the light beam off the ceiling, to flash-light and clear an entire room.
For open carry or bedside duty, I'd say light, laser and night sights!
For concealed carry, night sights and possibly a laser too! See Crimson Trace's DVD feature, Shots In The Dark!