I'm with GS in part because I have one of the CW stores in town and can justify paying their prices rather than waiting for Amazon to deliver. Plus there are enough Pilot and Flying J stations on our big trips to take advantage of the gas discount.
We tried KOA last year because we'd recoup the cost on a single trip to go see a niece graduate from college. Some of the CG's we'll visit again. I renewed this year just because they were offering a pre-paid debit card if you bought Allstate roadside service through them. More than paid for the membership.
We'll check into some of the other discount programss, but this year we're trying more non-traditional spots for camping. Several weeks ago we stayed at a ranch some friends rent for livestock, and soon we'll be visiting a friend's family property that has some RV hookups next to the manufactured home that is only used when they visit (it will be empty for our trip). Just trying out the right style of RVing that works for us.