And here’s Why ?
It is commonly assumed that the metal clevis is safer than the pop off type plastic clevis commonly found in model kits.
(Incidentally the plastic pop off type are intended for combat models)
<<<< METAL- vibration- METAL >>>>
But as is often the case metal clevis can loosen with vibration, even if crimped to fit the pushrod properly and fitted with a locking nut,
This metal to metal vibration can resonate forming a frequency that can interfere with the radio control system causing a glitch or even temporary loss of signal!
ball links roll within the nylon cup resistance free 360 degrees
AS USED IN R/C HELICOPTERS
And possibly the most significant point of all, it is rare to see a metal clevis on the swash plate of a full sized remote control helicopter!. because helicopters need smooth fluid control movement from ball links,And the heli pilots will not accept anything less than the best, so why should you