Ethereum is the best altcoin, it has great technology, many ICO projects use Ethereum's platform. Clearly Ethereum is worth the investment. However, if you choose between Ethereum and Bitcoin for long term investment then I would choose Bitcoin. Bitcoin is the king of the world cryptocurrency, it's very popular. I believe in the future Bitcoin will grow strongly and its price will go to the moon. Now is a good time to buy Bitcoin because the price is still low. Many experts predict that by the end of this year Bitcoin will reach over $ 20000