Good Sam discount is only 10% and generally comes on the nightly room charge, not after taxes are added, so that dilutes the 10%. And then, you'll suffer under tons of junk mail once you sign up that is ALMOST impossible to stop. Took over a year of sending it all back to them in their prepaid envelopes to get them to stop in my case.
Then they pulled a fast one a few years later and 'said' they were now associated with Passport American and since I was a PPA member, they had a offer for me! And here all their junk mail came again. PPA denied they were associated with GS so I have no idea what GS (or PPA) was trying to pull. I still have the GS form letter.
So stay away from GS, unless you like tons of junk mail.
But 50% off per night you get with Passport America card, now that's worth it. And very little junk mail. Save enough on a few nights staying at PPA parks during a trip to afford a 'resort' next to a golf course at full price. Yippee!
JMO