Both American Express Company (NYSE: AXP) and Discover Financial Services (NYSE: DFS) sport remarkably similar business models and, perhaps not coincidentally, have given investors almost identical returns over the past 12 months, both returning just over 22%. Which of these iconic companies makes for a better investment today?Let's take a closer look at each to see if we can arrive at a reasonable determination.Both American Express and Discover are their own credit-issuing financial institutions.