We have been RVing for over 30 years and have owned pretty much every campground membership program out there (TT, CTC, RPI, AOR, ROD). The main thing to look at is where the parks are located. The bottom line is: you have to use the memberships (camp a lot at the membership parks) to make them "work" for you. Otherwise you won't get your money's worth out of them.
We are now traveling less and only have the TT membership plus Passport America and Escapees memberships. We have had our Thousand Trails membership for over 20 years since we retired and figure that it has saved us several thousand dollars during that time frame - - but we have also stayed in TT parks for over 1,000 nights so far!