Both Visa (V -4.94%) and MasterCard (MA -5.45%) have consistently outperformed for investors, based on what many see as a rock-solid simple investing thesis: that these companies have nowhere to go but up as the world switches from cash transactions to credit. But is that thesis just a little too simple to be safe? And can the growth ahead really justify these very pricey multiples? In this video, Fool financial analysts Matt Koppenheffer and David Hanson discuss which of these two hot financial stocks is a more attractive buy today.