laser....the flashlight will show where you are and make you an easier target as well...but if you are in unfamiliar territory, a flashlight could help...I guess it depends on your application. Home defense where you know the layout and can hide? A laser to help make sure you are on target when you may not have a good sight picture or are stressed. Those are just my thoughts, I do not have any formal training or experience so take it for what its worth...
Only problem with this scenario is the fact that you may shoot a family member by not being able to identify the target.
A weapon mounted light will get you on target in the Home Defense ranges 99% of the time. If the light is shining on the target, you should hit it when you pull the trigger.
Another nice effect from a nice bright weapon light (in the 100+ lumens ballpark) is that if you hit the BG with the light and his vision has adapted to low light, it will stun them temporarily and disorient them. Usually for enough time for you to identify the target and make a snap decision to take the shot or not.
I guess this philosophy is why I have 4 weapons lights and ZERO lasers. I want to know who and what Im shooting should I ever have to.