Steem has the advantage of being a social media platform that produces high value content that automatically draws in users and investors even from beyond the cryptocurrency space. This has caused a viral effect for Steemit, reflected in the website being ranked < #10000 globally.
BitShares has the advantage of being a decentralized exchange that allows for trading of many different assets, enabling it to compete with major financial institutions and take on trillion-dollar markets like the derivatives-market. This is reflected in assets like bitUSD/bitGOLD that exist as genuine cryptocurrencies while tracking the respective values of USD/gold.
Both Steem and BitShares are good candidates for being billion dollar blockchains for different reasons. Their underlying technologies will allow them to scale to a global level, and they are backed by a pioneering and growing Graphene community of visionaries, developers, and entrepreneurs.
