You have to understand how lasers (LED's) work. Your bullet path is one line and the laser is at a different angle. So lasers are set a certain distance. They need to be sighted in just as scopes. If you are too far away your shot will be low, too close your shot will be high. For most applications lasers are less than useful.
The exception to that is CQB where distances are less than 50 feet. Lasers for pistols come from the factory set at 21 feet. Now, lights on a rifle or pistol will do you far more good than a laser, but it will also give your position away. A good set of night sights will increase your accuracy.
A battle rifle looks "COOL" with a laser on it, but in my opinion it is just for looks.
Jim
If your are getting a laser, get the green one, the red one is useless during the day in sunlight.