Talking about ball joints and the like, is permanently sealed better if one never greases them? My thoughts are the serviceable ones have to have a way of expelling the pumped out grease, which opens up the door to contamination as if grease can get out, other stuff can get in , while the sealed ones can be, well sealed and may be better off if neglected.
If you don’t intend to grease them, then get the sealed units. Not so much because of possible contamination, but because they are designed to last for a long time without maintenance.