For weapon lights, you want the ability to be able to turn them on and turn them off quickly. Some have the advantage of being left on and that is great for some situations (my rifle has it but not my shotgun, both dedicated lights). Understand that you want to be able to activitate the like immediately, with normal firing grip and deactivitate just the same. It is not always prudent to have a light on or off and so you want to be able to toggle as necessary.
For home work, I used the lights outside the home at night or only when going into a darkened room where upon I then activate the overhead light ASAP.
Why the overhead light? Weapon lights are a special tool that comes with significant advantages and disadvantages. The advantage is the option of having light anytime and anywhere. For example, mine came in useful checking noises in the attic at night where I don't have much lighting. It was an opossum. I crawled under rafters with my shotgun and its light before spotting the problem. Such lights are good for quick checks of things like closets where belongings may block closet lighting (see teenage daughters for reference).
The disadvantage is that weapon lights or any lights let the opposition know right where you are. I like the folks who think weapon lights give the bad guys an aiming point to shoot you squarely. If going against well trained bad guys, this is the case. For those righties using the FBI method of holding the light high and left of their body so bullets fly {supposedly} toward the light, when dealing with an untrained rightie bad guy with a flinch, shots aimed toward your high left will impact to his low left...not good. Anyway, that is part of the reason for the need to be able to turn off the light quickly, regardless of where deployed from your person.
I have met folks at Thunder Ranch (NOT instructors) who stated and had trained themselves in clearing their homes with weapon lights because they knew to be true that they knew their house better than anyone else and they could be their own sort of masters of the night in their own homes with weapon or handheld lights. This is stupid. Bad guys don't need intimate knowledge of your home to hide behind a couch, wait for you and your light, and unless you sweep their position the very first thing and find them peeking around the couch with their gun, then they have the advantage because those clearing rooms with lights focus on the illuminated area. So long as the bad guy is in the dark, he feel safe. He knows exactly where you are and you are clueless as to his location. Weapon lights and dark rooms work well with SWAT teams who have members that each have designated areas of illumination and coverage. Most home operaters are single units, not teams. SWAT teams use said lights as they can never count on a suspect's home being properly illuminated with interior lighting or even electricity. So they have to utilize weapon and handheld lights as primary lighting for the initial entry/confrontation. Notice in documentaries that when possible, they opt for interior lighting for the later business and final securing because on a broad scale, standard interior lighting is better overall, but still may need to be supplemented, so they still use weapon and handheld lights as needed.
So the overhead light sort of equals up things between the homeowner and the intruder, sort of light dealing with a person in the day time. Critically, it helps give the homeowner peripheral lighting that might be critical in not only locating the intruder, but potentially instruderS if the intruder isn't alone. Target fixation is bad enough in regular lighting and is reported to be that much worse when all the good guy has is a narrow beam flashlight.
Weapon or handheld lights for home defense situations should be utilized as situation-specific tools AS NEEDED, only turned on when needed, and not and the full time primary lighting unless that is what is needed.
