I searched MANY structures, and built-up areas, in 33+ years of big-city police patrol. (This does not make me an expert.) Some thoughts:
For those who believe that anyone inside your residence can ONLY an intruder, well, during one foot chase, the criminal smashed THROUGH a glass exterior door, into an occupied residence, and duty compelled me to remain right behind him. The couple, inside the home, were QUITE surprised to see this happening. Fortunately, there was enough lighting for them to understand what was happening. I was too close, on his tail, for the criminal to try grabbing a hostage, and, cornered/trapped, he disappeared under a dog-pile of officers.
A hand-held light is vital. A spare hand-held light is a very desirable option. A WML is somewhere farther down the list.
In a dynamic encounter, where I cannot be sure whether or not the enemy might be behind me, which includes my flanks, tritium sights can be a liability. This is not theory; the fresh green glowing vials, in my rookie trainees’ sights, as I evaluated their building searches, were like Rudolph’s Red Nose, making it easy for me to track the trainees, without having to use my hand-held white light. (I would not want to back-light a fellow officer, for obvious tactical reasons.) Now, if one were to remove me from that equation, at that moment in time, and insert an armed felon, well, we see the liability that tritium sights present.
So, I believe that a WML is more important than tritium inserts in the weapon’s sights. Both are optional, and, if I am hunting bad guys, in a 360-degree-threat environment, I would rather that my weapon’s sights not glow. Again, if I am hunting bad guys, in a 360-degree-threat environment, I would rather that my weapon’s sights NOT glow.
More than anything else, tritium sights helped my aging eyes “game” quals, and one or two “tactical” shooting exercises, because I could align the glowing dots, rather than have to focus sharply on the outline of the sights. In real-life encounters, it was having a white light that mattered.
In most circumstances that justified pointing a firearm at a person, I could see him, and he could see me. A WML would not be “giving away” my position, at these times, but might well be what would enable me to see his hands well enough to know whether he presented a deadly threat. (In actual practice, during most of my career, I was not allowed to use WMLs on any duty or defensive firearms, on or off the clock. When more than a handful of officers, which included myself, started using WMLs, the command staff banned them, pending “study.” After years of “study,” WML protocols were developed, then studied by city legal, which took more time. Finally, training classes were developed, to certify officers to use WMLs. I never played golf with right folks, or learned the secret handshake, or whatever, so finished my career with my firearms “slick;” no WMLs, lasers, or optics.)
WML on my home-defense firearm? Short version: Yes, of course. (Longer version may follow. Or, not, as others may well have covered it thoroughly.)