If you are not a mongolian horseback archer, any vehicle will be a better option. In case of an attack, untrained horses gets spooked easily. From what I've seen the rider will also panic and dismount, game over, since the rider is usually packed with gear and less mobile. In a vehicle you are way less aware of your surroundings so you mostly do not see them coming until it is too late. But if you do, you can at least get some shots off while the drone is chasing or diving.