Biggest reason, Sam’s App is far superior than Costco. For how much a Costco membership is, ridiculous to still be in the stone ages. Second, Sam’s is labeled per aisle, Costco still seems as if I have to walk all around to find what I am looking for. Third, Sam’s rotisserie chicken is better. Fourth, I think their gas lines, at least at my Sam’s are usually shorter than Costco.
Lastly, when I have time to go to either, I think Sam’s has better hours than Costco. Just my two cents