There also seems to me to be a pecking order of how you can expect to be greeted, accepted or treated at parks with other affiliations. That is the way the park members want it. That's about the order of their own membership affiliation and thus is their priority. We also have a KOA discount membership card at about the same price per year. Also reservations are never in question if you hold their minimal costing membership cards.
Escapees has a park system of their own.
The most lavish is the original one in Livingstion, Texas. We most definitely belong to Escapees. They are wonderful for the extended or fulltime RVer. They offer a great mail forwarding service, which is our address and they offer many other RVer services. We didn't originally join them for their park system, but now enjoy them fully, if we are going to be in an area where one is.