You guys are missing the point or do not understand how to use a polarizing filter and or an ND filter. Forget drones and think of a camera and a scene. A polarizing filter, linear or circular, can only work on the camera in your hand, when you point it in the direct that it will have an effect. Therefore, the filter will have a greater effect in a certain angle of direction to the sun, than in the other angle range of direction from where you are standing and your subject is placed in relation to the sun.
Therefore, in the very same way, the filter will show a greater or lesser effect in the image (either still or video) when you are flying or photographing the subject in one direct and position to the sun with the filter fitted but should you turn and fly in, say, the opposite direction, the filter will have a different effect on your image. Now, an ND filter affects the way the light comes through the camera lens and therefore, shows this affect no matter which way the camera is pointed during flight, it simply restricts the light falling on the sensor of the camera.
You can not compare an ND filter to a polarizing filter because these are two completely different filters and used for two completely different things. It is sort of like cooking dinner then adding water or sugar to the dinner. Both will alter the dinner but not in the same way and both are used for different purposes in your cooking, you just can't expect to compare them to each other and ask yourself which one is better. Hope you all now understand what you use a polarizing filter for and what you use an ND filter for. The only thing they have in common with each other is the fact that the word filter is used when naming them, but it ends there.