Unfortunately, like with lenses, the better the filters cost a lot more but are usually worth it. For video it comes down to a tree off.
You have to weigh the benefits of using an ND with the down side.
Of course the benefit is being able to keep shutter to the '180 degree' rule, but the other benefit is that it eliminates the risk of jello.
For me, I use a 16 on bright sunny days to keep my shutter at 60. I use the Polar pro set which seems to be ok for its price point. I also reduce contrast and sharpness and saturation some (all great tips found on this forum), then bring it all back up in post. Not 'film, quality, but I usually do commercial real estate work.
On overcast days I sometimes don't use ND at all because there's lower risk of jello and I can get better colors.
As you may know, if you don't use ND and you don't get jello, the video will, arguably, be too clear. Viewers are used to a certain amount of blur (thanks to film) so when video is too clear it gives it a Soap Opera effect.
With 60 and 120hz TVs and Clear Motion, I think that may be changing though.
I would think Shooting sports would benefit from faster shutter speeds but you still have to worry about jello.