Upright antennas will yield higher coverage with less antenas. Slanted antennas will limit the amount of non useful RF escaping upwards into airplanes' radomes

Upright antennas will yield higher coverage with less antenas. Slanted antennas will limit the amount of non useful RF escaping upwards into airplanes' radomes but will have a range limited by the slanting + beamforming angles. An analogy is having public lighting with the bulb focused horizontally versus focused downwards. If it is facing horizontally the light will illuminate farther but a fraction of the light will be light pollution pointed at the night sky. If the light is facing downwards it will be limited by the aperture of the lamp post holder.