Try going with a friend to a Costco, and compare the products available. I find that Costco has better quality items, and their house brand - Kirkland - to be fantastic for all kinds of things.

I find it hard to believe that anyone whose really explored both would be content with Sams Club which is basically a narrow subset of Walmart goods.

Maybe if you're doing a lot of MS, Sam's has some value with its appearance on some CB apps, but I don't think that applies to most people. (not for me at least)

For their most elite, valued members Costco recognizes them with special treatment and the 'Executive' notation on their card.

I'd advocate more for them, but the parking is bad enough as it is.