Steem ! No Doubt ! It is the only currency which is backed by a strong business model. Steem blockchain empowers the blogging mechanism and the dApps built on the Steem blockchain such as dTube, Musing compete with the mainstream giants such as Youtube and Quora.
Once the Smart Media Tokens are out probably all the major blogs will start rewarding their influencers and authors in the crypto currencies if their business model justifies.
Its expected that if the SMTs become reality then SMT will change the business model completely and the prices of Steem would also be skyrocketing. Hence i guess it would have a significant impact on the crypto currency businesses. I think Steem would be long term sustainable crypto currency