Free Your Mind was popular back when I was still in junior high.
Fun song.
I use debit, primarily because I'm more conscious at any given point of my checking account than my credit limit, and in any case, I tend, because i'm a bozo, to keep a balance on my credit cards.
I'd bet that stores get a better merchant rate on debit cards than credit; typically the more verification information they can get from you, the better, and debit cards have both the big whammy of trust: the PIN; as well as the important factor of having the card (which is more trustworthy than typing in the card number). Machines that don't ask you whether your card is debit or credit will always go debit on a debit card with a credit-card logo, which is the reason I have this theory.
I use credit cards simply because of the benefits of the cards (1-3% cash back). No other reason.
Most debit cards can be used as a credit card or as a debit card. It's cheaper for your bank if you use it as credit, but cheaper for the store if you use it as debit. In my case, my bank gives me cash back if I use it as credit, so I always do that. I've even seen some banks that charge a fee for each debit purchase. It's getting harder and harder to use the card as credit, though, because most stores' swipe machines automatically assume you're using it as debit (remember, it's cheaper for the store), and some make it really hard to figure out how to use credit.
I've seen a great increase in debit usage at my store. I think that it's largely people who've accumulated a lot of revolving credit card debt. They can't bury themselves if they can only spend the money they already have.
For a store, it costs 35 cents to swipe a debit card; credit is 35c plus 3% of the sale's total (5% for American Express, which is why so many places won't take AmEx, or set a minimum purchase amount to use it).
Those costs are typical, but not universal-- my employer pays less than 3% when we have the card or we can confirm the buyer's house # and zip-code. In the future we'll be able to accept that novel 3-digit number that websites often ask for, and we'll get an even lower rate.
But because of the nature of my job, I never have the card in hand and sometimes don't have the address info easily at hand, so I weigh the value of my time in getting the info versus the value of money saved by my getting it.
Debit. When they first came out, there was a fee to the customer to use them as credit cards. Haven't checked in a long time to see it this is still so. I have never had a credit card and don't intend to get one. I think they encourage bad spending habits, as well as being a ripoff, Cash back? They're luring you to spend more than you need. Theft protection? Most Debit cards have that now. Emergency use? How about SAVING money to an emergency fund?
I use debit because it's quicker to enter my PIN than sign my name.
Debit: I hate spending money on interest and using the debit card cuts down on the chance of me not using the credit card.
Hmm... cash for small purchases, debit for low value stuff & groceries (get bonus points), credit for higher value, online & gas (get bonus points). A lot of it is habit & I haven't really tried to figure out the logic of why I grab one and not the other.