This is much more efficient than using the true magnitude in the comparison.
Sometimes, the overground heading to a target is required. For example, imagine a player standing on the ground who needs to approach a target floating in the air. If you subtract the player’s position from the target’s then the resulting vector will point upwards towards the target. This is not suitable for orienting the player’s transform since he will also point upwards; what is really needed is a vector from the player’s position to the position on the ground directly below the target. This is easily obtained by taking the result of the subtraction and setting the Y coordinate to zero:-