In many cases, taking aerial video the camera isn't always going to pointed in the same orientation from the sun.  So the polarization filter effect could change throughout the video because when doing aerial you can't turn the filter as opposed to a hand held camera.

So would it be better to purchase ND filters without polarization or is the potential for uneven shots negligible or not very noticeable that the benefit of the polarization to filter reflections outweighs the potential drawbacks in shots where the orientation changes?

Great Question, if you set the polarizer to a linear orientation you should be ok with changing direction. The linear setting covers the broadest range of reflections, even when it is not at the max polarization angle, it will still reduce some reflections helping increase color saturation. Occasionally you can get a little color shift in the sky when the sun is setting or rising, in which case a straight ND may be useful. But when the sun is up in the sky I always have my ND8/PL or ND16/PL on.

A lot of people have both the Cinema Series Vivid Collection and Cinema Series Shutter Collection of filters to have the options.

Let me know if you have any other questions,

Jeff

Jeff-
I just got the P3P filter 6 pack. How do I tell what the linear orientation is? Is there a mark on the filter?