In many ways, Costco (NASDAQ:COST) and Wal-Mart's Sam's Club are interchangeable. Both have their supporters who would tell you why one is better than the other, but at the end of the day, both warehouse clubs offer discounts on a wide range of items to people who pay a membership fee.

One chain may have a better price on tubs of mayonnaise while the other offers a great deal on snow tires, but those are moving targets which change regularly. It's hard to compare the two warehouse clubs on the basis of any specific savings because an item sold at a good price one day may not even be offered the next.

But one area where both companies can be compared is their rewards credit cards. Sam's has its Sam's Savings MasterCard (NYSE:MA) while Costco launches its new Costco Anywhere Visa (NYSE:V) June 20. While the two warehouse clubs also offer different deals for business members, this comparison will look at what each rewards credit card offers to individual members.

Both Costco and Sam's Club offer rewards credit cards. Image source: Sam's Club.

What is Costco offering?

In switching its credit card from American Express to Visa, Costco upped its rewards game. The new card has no annual fee on its own but requires that holders pay the warehouse club's $55 annual Gold Star membership charge.

Members who hold the card get 4% back on eligible gas purchases (for the first $7,000 spent in a year; then it drops to 1%). They also receive 3% cash back on purchases made at restaurants and eligible travel and they earn 2% cash back on all Costco purchases, as well as 1% back on anything else bought with the card. Cardholders also get worldwide car rental insurance and worldwide travel accident insurance as well as damage and theft protection for some purchases.

Costco does not list a maximum on total rewards that can be earned through its program on the Citigroup (NYSE:C) web page that details the terms and conditions of the credit card offer. A request to clarify that there was no rewards limit through Citigroup's Twitter support (which is where the card issuer directs consumers looking for more help) was directed to a different web page, which also does not mention any annual rewards limit except capping the gas reward.

What does Sam's Club offer?

A basic Sam's Club annual membership costs $45, or $10 less than its rival charges. Of course, to get a credit card you must hold a valid membership.

If a Sam's member spends $100 on the day he or she opens his or her Sam's Savings MasterCard account, he or she gets credited $40 on that initial purchase. Members also get 5% back on gas -- up to $6,000 a year (then it drops to 1% with no limit), 3% back on dining and travel, and 1% back on all other purchases. Cardholders also receive price protection on some purchases as well as identity theft resolution services.

A maximum of $5,000 in cash back rewards can be earned in a calendar year.

Which is the better deal?

Both companies have very similar offers with nearly identical basic rewards. Sam's however has cheaper membership in general and offers $40 back if a new member spends $100 on the first day. That's enough to make its card a better deal for most people.

Of course, as is the case with all credit card offers, rewards programs only make sense for people who do not carry a balance. If you don't pay off what you owe each month, thrn interest charges will quickly negatively offset any value received from getting cash back or other rewards.

While Sam's offers the initial cash back, which makes its card a better offer for many people, it does cap overall rewards, which Costco's card does not. That means that for heavy spenders -- people who will buy enough to earn more than $5,000 annually -- Costco offers a better deal.

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