Bitcoin is the one. It will always be the gem, the most precious one. Great for an investition.
On the other hand, Ethereum has two years of prosperity. It is the useful, the one that is ready to serve the general public's needs.
But Steem rises. And is on its way to became the currency of future. It is even more useful and handy then Ethereum. Plus it is social. Invest into Steem if you can.