"Visa was an early mover and they built share in signature debit quicker than MasterCard, and they dominate today," said Thomas McCrohan, managing director of equity research at Janney Montgomery Scott LLC.
MasterCard, meanwhile, said it's also done significant work "to expand debit card acceptance" and that it's continuing to grow its debit business, including a recent deal with SunTrust bank to issue five million new MasterCard debit cards.
Banks like SunTrust, analysts say, have an incentive to issue debit cards because they're less risky than credit cards -- credit card defaults skyrocketed during the recession -- while providing a revenue source through interchange fees, the fees that banks charge merchants for every plastic transaction.
Debit card users, meanwhile, may continue to rely on their cards for reasons that extend beyond post-recession prudence. For one thing, the losses suffered by banks in their credit card portfolios and recent credit card reform rules have meant that credit cards today are much harder to get than debit cards, said Bill Hardekopf, CEO of the card comparison Web site LowCards.com.
"Some of it has been forced on the consumer," Hardekopf said, "Credit card issuers have cancelled a great number of accounts. They have cut the credit limits on millions and millions of credit card holders, so people can't charge as much as they used to, and credit card issuers have tightened their approval rate."
And then there are the benefits of going cashless.
"It is just so much easier than consistently carrying around cash all the time," Patel said.
Whatever the motivation behind debit card growth, for credit card companies, it's been a bright spot at a time of shrinking U.S. credit card revenues.
"I'd prefer that they were both growing," Murphy said, "but I'll take one."