BTC is considered the main cryptocurrency. It is the one with the highest capitalization.
But Fundamentally there exists no basis for price discovery so other than pure speculation I can’t see it being a viable store of wealth by any measure.
And with central banks such as China now openly researching and testing block-chain as a solution for digitization of their currency, the way I see is that third party or independent currencies such as Bitcoin will continue to struggle to gain true dominance globally as a store of wealth in the long run.
Steem on the other hand would make a better investment than any other as of now in my opinion as it is backed by this decentralized platform.