The majority of all lights are unsuitable because they  reflect a part of light into the sky. The part of light which is above the horizontal line ( see the picture) is useless and disturbing for its surroundings. This part of light energy is completely wasted.

Everything considered  we can conclude that these lamps are the biggest light pollutants, of which non cutoff lamps are worse.

We can distinguish non cutoff lamps from cutoff lamps because they have round convex glass  which stands out of the casing.