I will say they are way better quality than red ball, seem to be more UV resistant
The main difference is the actual material used. We use the most chemically resistant material out there (Super secret, so can't say what kind), but gives what we've found the best clarity when dealing with the widest range of chemicals.
There are still a few chemicals that are pretty darn rough on it, but there hasn't been a plastic that performs better over the spectrum of chemicals, while still giving a clear sight.
UV is also the main factor in them getting cloudy as well, so someone in Northern Canada will tend to see more use out of them before they get too cloudy versus someone in Arizona.
If they do get fairly cloudy, as a 'one-time' fix/improvement, some guys buff them out with the 3M de-fogger that they use on scratched/faded vehicle lights. Seems like this only works once, but then reapplication just seems to scratch it and not improve it much.
Used them for the first time last year on the primary liquid fertilizer runs of my drill. I noticed some balls (steel) will spin around the inside the indicator and others will bob up and down. Even though flow is equal the different behaviors cause the balls to be at different heights inside the indicator.
Any way of getting all balls to either spin or bob, But not both?
Depending on how your plumbing is stacked (how many manifold flow indicators you see lined up to each other), it can vary how the balls react a little bit. Typically, I'd recommend having a max run of 3-4 on each side of a wye (like the picture in the first post). This tends to give the balls (for the most part) a more even height. The stainless balls should be perfectly round as well, so it shouldn't have anything done with the sizing/weight of balls being off either.
Let me know what you had setup, and it might show into what can be done to help it.