Credit card companies are constantly enticing consumers with offers to switch the plastic in their wallets. What keeps people loyal? New York City-based Brand Keys interviewed 400 credit card users to determine the attitudinal and behavioral factors that influence their decisions in the category. Out of several dozen attributes, Brand Keys identified four key drivers and scored them on an index of 100. The survey participants, 100 per brand, then rated their card of choice against these top attributes. Discover led the way, especially in the fees and rates category, where customers praised its cash-back rewards program. American Express clients appreciated their extra perks, like reserved ticketing at premier events, but wished more places accepted the card.