Understand that RPI and C2C are networks that you can join only after buying a membership in a member private park. If you buy a membership in a park that participates in both networks, you can join both networks, otherwise you can only join the network that your "home" park belongs to. Membership in these networks allows you to stay in member parks for one week for $10/night although there are often hefty surcharges for 50 amp power. Some parks open only their less desirable sites to RPI and C2C guests. There are various levels of optional memberships that allow longer stays.
We joined RPI and C2C in 2004. We dropped RPI a few years ago because they do not have an online reservation system and there is a great deal of overlap between the two networks. If a park is in the RPI directory, chances are its in the C2C network as well.
Since these are all private parks, they are mostly "destinations," not places to stop on the way to someplace else. In other words, they are usually off the beaten path.
Given all that, I would say that RPI and C2C are worth looking at if you are a fulltimer and if you can find a home park that is reasonably priced, has low annual dues, and allows you to drop out whenever you want.
You can see the C2C directory here: C2C Directory
. The parks that are listed as "Classic" or "Deluxe" are available to all C2C members. Note that there are only around 200 of those. The "GNP" parks are public parks that offer a $15/night rate to C2C members.
We use C2C only two or three weeks a year now, but that's enough to make the annual dues worthwhile.