I have an 870 and a few others too but I am not interested in any light or electronic sights. Maybe I am in the minority here but I always want to literally remain in the dark and not give my position away at night with a light. IMHO, a bad guy will naturally shoot at the light or laser source - something I think is a bad situation. If you are aiming the gun then that means the light is right between your eyes - perfect head shot target for the bad guy!
My solution...... I have four 2 watt equivalent LED night lights strategically placed in our home. They are very very dim however because it's our home I know the layout - every square inch and my eyes would more than likely be adjusted to the dark - not his. An intruder does not know the layout and while the night lights would benefit me greatly, it would not do much for the bad guy. IMHO this is a better solution for me. Same case with a hand gun - no light or laser on it. I do have a small and powerful flashlight right next to my pistol to grab, but I would hold it out as far as my arm would go before turning it on if needed. Like police training did in the 70's and 80's.
IMHO, the light attached to a pistol is more about selling lights than self defense common sense - but I for one, am not buying all the hype! So is my theory a good one or a bad one? You decide.