I was playing around with a buddy's laser sight the other day. My impression was that it slowed me down because I was trying to find the red dot across the room. For what it's worth, I find that most new shooters I take to the range miss the target because they flinch and drop the pistol down, jerk the trigger, or fail to use the correct stance, not because of sight alignment issues. Lasers don't fix any of these problems.
If a room is black, it would be better, but, again, there are night sights and they don't add any extra bulk or weight, nor require batteries. Either way, if you actually want to see and identify your target, then your pistol is going to need some sort of light as opposed to a laser.