I say if you have either a Sam's Club Discover or a Walmart Discover...you're good. You don't really need both b/c they can be used at both stores. I'd have gone for just the Walmart Discover b/c they have the free monthly TU Fico.
For me personally, when I think of places like Costco or Sams Club, MY intent is to use their cc for household products and food & beverages. When I think of WalMart, I think electronics. Am I trying to justify the fact that I have a Wally Discover AND Sam's CC? Possibly.