i dunno, maybe it depends on each person, but in the tests i did i was consistently more accurate (though maybe slightly slower) with the laser than without it.

the test i did was to run 1KM as fast as i could, uphill, get the shotgun off my back, spin around a few times with my eyes closed then take a shot at a target i had set up on a tree.

maybe it sounds ridiculous but i think that the extreme heart pounding and the dizziness simulate a massive adrenaline dump fairly well. it was also freezing cold when i did this, without gloves, so i figure i lost a lot of finger dexterity as well. without the laser i had a lot more shots hitting the fringes of the target rather than the center of it. with the laser i don't think i missed even one time.

laser also has the benefit of letting you fire from the hip rather than through the sights. even at close range without sighting a target, a hit is not a guarantee - someone at the end of a hallway is just small enough to be missed by a panicky quick shot. just my opinion tho!