To the OP - It has a lot to do with what kind of light you have attached to your handgun. Lets just assume your talking about something like a surefire white light rig.
1. If your in 100% total darkness where you cant see your hand in front of your face (unlikely) then the act of turning the light on places you at a disadvantage. The bad guy will know exactly where you are before you know where he is.
2, If your in 100% total darkness the bad guy cant see you any better. Your number one asset at that point is your hearing - you need to ID approximate location before you go turning on a light.
3. If your in 100% total darkness and your LE and you take a shot without seeing hands your in deep $H1T.
4. Realistically it going to be a low light confrontation as opposed to a no light confrontation. Weather or not you hit that remote switch is going to depend on how low light. Question is : how sure are you that the dark blob in front of you is the threat?
5. Point>Illuminate>ID>engage (dependent on your ID of course) . After that you have some decision to make based on whether or not it was a single intruder, or your confidence that the threat has been neutralized.
Do you want to keep the light on longer to ensure the threat is gone or do you want to continue the clear to ensure ALL the threats are gone?
No matter what I write or anyone else writes ref white light shooting there will be disagreements ad nauseum. I can come up with a zillion different scenarios that will either support or destroy different techniques (mine included).
In other words If your in a no-light low-light engagement you have stepped into a bad situation.
If you really really really want to be the night avenger get some genIV Night vision and either an I.R. light or better yet an I.R. Laser (might as well go with a suppressed weapon) and you will come out on top of a low-light/no-light fight every time :-)
barring that - its a crap shoot
If someone wants to start a thread on handheld light - I'll be happy to discuss the advantages and disadvantages of the Ayoob, OK , Offset, parrallel, team illume techniques of night fire. :-)