None of my firearms have any rail lights. I don't even own a light I could put on the rail, well without using duct tape that is.
I can see just fine in my house at night the vast majority of the time between ambient light from outside and the multitude of lights inside (clocks, DVR's, electronics etc). For those rare occurrences, maybe a power outage in a thunderstorm I have a handheld flashlight. Speaking form a purely tactical calculation as Sun Tsu would say, in my home I have the advantage over the terrain which gives me an edge from the start. In my opinion I loose some of that advantage with a light shining.
If I was going into somewhere unknown that would change the calculus. But for home defence I never saw the need for a light beyond a handheld one in those rare instances I mentioned above.
I would go with handheld over rail mounted for home. It gives you more versatility in my opinion.
Just my 2¢.