Precision aim, versus a spinning trimmer that cuts a whole swath. The inverse kinematics of the system are a lot easier. Distance. The laser and aiming mirrors

Precision aim, versus a spinning trimmer that cuts a whole swath. The inverse kinematics of the system are a lot easier. Distance. The laser and aiming mirrors can all be up in the body, while the beam reaches the dirty work. Energy efficiency. It might be that the total energy to bring a motor up to speed and swing the arm at the weed may be greater than a brief zap with a laser, even if the instantaneous power of the laser is much higher. Certainty. A string trimmer takes a certain amount of nuance to start gently so you don't bog down the string, advance through the weed, and understand when it's done. A laser can just run at a fixed power and scan speed, and almost certainly produce the desired results. Frickin' lasers. There's PR value to that.