the rolling ball ones...especially the RULE ones for the last decade or so have been problematic in 2 areas...the balls themselves get dead spots on them...probably from arcing and the floats themselves if subjected to typical bilge slime do get sticky enough to "not float".
I agree that the air ones and some of the electronic ones do have their advantages but alas they too can have failures (even though you have not experienced one - yet).
My solution is just buy a couple of the cheaper ones...whatever suits your fancy or even try 2 different styles....connect both to the pump, one higher and out of the goo so to speak...the higher one should not suffer the same fate of the lower one and be a backup just in case.
Of all the safety precautions we as boaters take...I'm not sure why this simple yet effective solution isn't explored more.
Hook the higher one to the high water alarm system as an added benefit.
2 switches works for safety, but 1 more switch plus 1 more pump is better.
I just bought a SPX-Johnson AS888 rolling ball switch cheap off ebay.
I plan to use a 40 amp cube relay to reduce the load on the switch for a Rule 3700 pump.
Switch was said to have a microswitch that the rolling ball whacks.
You have to loop the wire which allows float to lift. I did not like their solution of a small slot under the base, wire can fall out of place.
So I drilled 2 small holes, passed wire thru then hotglued to secure so when I screw it down wires wont be out of place.
Other thing, this may have issue shutting pump off. When float falls down, it has to be almost touching the surface it is mounted on. A pump can not pump that low. So I will put something under the switch mount screws to lift it higher to ensure a turn off.
I figure the relay will take the load and lengthen life of the switch.
This switch design is better than the sealed shaft switch that seal can fail and water leaks into the float where it has electrical points. I had two of those type fail. The shaft seal leaked, shaft corroded, one float stuck, other one switch points rusted.
This SPX switch, a weakness is wires can break over long time float moving. At least there is no rubber seal sealing metal shaft.