American Express and Costco have what it takes to reward their customers and shareholders over the long term. Here's how American Express and Costco are building out their loyal customer bases, and why both dividend stocks may be worth buying even if the S&P 500 sells off next year. American Express' brilliant business modelConsumers turn to American Express for its perks and exceptional rewards program, even though the annual fees on its cards can be hundreds of dollars. American Express has around a 2% net write-off rate, which is exceptional given its flexible spending limit. Investors who don't mind paying up for quality may want to buy both stocks, whereas value-focused investors may want to go with American Express over Costco.