In a class I was in at Blackwater, we spent part of a day in a dark "shoot house" exploring the "sights vs laser" debate (which, IMHO goes along with 9MM/.40, semi-auto/revolver, etc.). Two things we discovered: Shooters would move their focus from the target, to the laser beam , and then their eyes would follow the laser beam to the target, breaking the total focus I would want on the target.
When shooting force on force "sims", we found out two things: With a moving, human target, the shooter would still focus their attention on the beam, instead of the threat, and the moving, "screaming at you threat" didn't even notice that the beam was on them. (And think about keeping a beam on a moving target-at least in my experience, I was watching where the beam was pointed, more than on the moving target.)
Another observation: During a recent day at the range, two bays down from me a guy was teaching his girlfriend how to shoot, using a Glock 19, with a laser. All the beam did was confuse her, as it seemed to be one more thing she had to look for. I used this as a "teachable moment", and got her using a G19, without the laser, then her boyfriends' gun. In this instance, sights were easier for her.
In any of the schools I've been to thru the years, no instructor, or staff person I've had the privilige to work with has had a laser equipped gun. The one comment that I remember about all of this that stands out came from Clint Smith at TR, when during a break, the class was having the "caliber-laser-type of gun" discussion. Clint said, "Whatever system you choose is up to you. Chances are that the rest of us won't be there when you really need it. Remember that your life could depend on your choice".
One possible test could be for someone to use a laser in a class (like mine, or similar), getting away from a "controlled environment", then report back.
Again, this is all just my humble opinion.
Don