I think Bitcoin can do both, and that these different aspects of Bitcoin actually reinforce each other. I also do not think Bitcoin will become a world reserve currency without experiencing mass adoption as a currency for the people first, history also certainly supports this theory as well.
It doesn't.
Typically any form of money that is not fiat started gaining traction as a currency only because people tended to hold it as they considered it valuable.
You should check your history, gold and silver coins have been used as a currency and a commodity for the majority of our known history.