debit or credit

Debit is lower fees for the merchant


That's the main thing I can think of

Credit offers more protection to the consumer.

Debit is only for those who cannot control or get credit.

Debit is you personally guaranteeing payment to merchant while credit is a third party guaranteeing payment to merchant. If you have adequate funds in the account then the transactions should be handled the same since the institution issuing credit on your behalf has means for instantaneous repayment. It is only when you have inadequate funds when it should make a difference. What are the fees for overdraft protection versus the interest cost on borrowing, and what are the limits of each?

I pretty much only use debit now at SAMs because I don't have MC or discover

Credit you get reward points. A debit gets you nothing. You should only use a debit card if you cannot control your spending. No one should even own a credit card unless they plan on fully paying it off every single month (unless your interest rate is 0)