We are thinking about getting a membership to one of the above listed places. I've never been to any of them.
My mom already has a membership to BJ's so she could add me onto her plan for about half the cost of signing up on my own. Sam's Club also has a Groupon right now for a reduced cost on membership. I always see people on here raving about Costco though! Is it really that much better? Is it worth paying twice the cost of the other two?