Even though Walmart's ( WMT) Sam’s Club is one of the top warehouse clubs in the country, it still wanes in popularity when compared to its top competitor Costco ( COST) . Sam’s Club currently has an estimated market share of about 31% compared to Costco’s 61%, and it has roughly 69 million members, while Costco has about 132 million.

LOUISVILLE, Ky. (WDRB) -- Sam's Club and Costco have just announced big changes that longtime customers are very unhappy with. Both stores have made changes to their membership agreements. If you have a big family, members say it's hard to beat Sam's Club with big savings on bulk items - from detergent to frozen food.

Of course, Costco isn't the only big name in the warehouse club space. Sam's Club has long been a huge Costco rival. And at a lower price point for memberships, it's easy to see why Sam's Club is able to take some of Costco's business away.

Warehouse clubs don't play by the same rules as other retailers. Because people pay to join Costco and Walmart's Sam's Clubs, both companies have a different relationship with their members compared to rivals like Target, or regional grocery chains.

When it comes to Sam's Club versus Costco, many people have strong opinions. This can make it hard to decide which club to give your money to, as your friends and family may be divided. Both