If you are building a card reader, be aware that all contact points must be in high impedance mode until the card is fully inserted into the reader. Otherwise some inputs will be shorted, voltage applied to the "wrong" inputs and so on. There is usually a switch that senses when the card is fully inserted, and it is safe to apply VDD, clocks and so on.
I'd go for the interface circuit since it solves all these problems.
For tests & experiments it's possible to hook it up directly to a MCU but then you need to rewrite everything when you add an interface circuit in the real application. In my experience, it's not worth it.
