I use Stix and Nauticam carbon float arms depending on circumstance. The Stix are used on ULCS or Nauticam arms. The Stix are nice because they are light and fairly small and can be quickly changed around as needed. I use the jumbo size have cut some in half so I have more flexibility. The Nauticam arms are bulky and expensive, but their buoyancy does not change, they don't stay wet and are easy to rinse.
I tried a couple kraken adjustable float arms, but one of them leaked during the warranty period and the seller said to take it up with the manufacturer and the manufacturer never responded to phone calls or emails, so I won't do that again.
But, there are a few quirks with the Stix; somewhere below 100' they will compress and once they do, even if they return to normal shape, they seem to compress more readily in the future at shallower depths. In that regard they do sort of have a useful lifespan after which their value diminishes. On a recent trip my son's Stix arms compressed even though we never were below about 80.' I suspect they must of been damaged on an earlier trip but am not sure. It did not make a critical difference in their use, though. Maybe after a few years they become susceptible to compression without ever being taken deep?
At the end of a dive trip they can be slow to dry which might be is an issue for packing, and sometimes it seems that salt cannot is hard to fully wash off or out of the floats and a salt residue can appear, if that matters to you. Following a dive trip, I soak Stix in warmish water fully submerged. I change the water once or twice over then next couple of days, and that seems to help get them clean.
I have not used them but I think the Inon megas are good, from what I have heard, if their length and weight options work for you.