If you trust your smartphone then you don't necessarily need smartcards. But if you want to run own applications in a trusted environment then JavaCards are really nice. You can also use them as a portable trusted "computer", wallet, ...

In terms of use, there's an additional complexity for using JavaCards. We try to solve that a) making the code easier to port and b) providing access to smartcards via TCP/IP where it makes sense to have them in a rack.

In general, they don't run out of battery and you can print your headshot and name on them.

In terms of "hardware" - all chip debit/credit cards use the same processors (actually they are a complete computers with EEPROM, RAM, co-processors).