I used to belong to Sam's. I find Costco cleaner and better organized, the people are more helpful, the products and prices are pretty much the same, and Costco runs specials that allows me to save even more.
My In-laws use Sam's Club...they have some different brands but I agree, I would much rather shop in a Costco then Sam's. They are always so crowded, dirty, etc. And I love their hot dogs. :)