[master5o1]

Developers are still more likely to implement the one API that provides n payment methods than implement n APIs to get n payment methods.

That is, a payment processor like Stripe that provides AMEX, MC, Bitcoin or what ever is often more valuable than by being able to reduce complexity in the integration of services.

[rubyfan]

Right, it's not a choice of picking MasterCard's one API vs. Stripe (as an example)

It's Stripe vs. implementing 10ish card or payment APIs. The choice is easy and will continue to be for most consumer facing scenarios.