Costco or Sam’s?!

I need to buy in bulk (we are a family of 6). I’m not sure which one to go with. My parents have a Costco membership so I looked around at groceries on their site and compared to Sam’s listings online. Sam’s membership is cheaper, they seem to have a better variety and their products even seem cheaper. But so many people seem to like Costco more?? Which one do you prefer and why?? I need help making my decision