Diversity is the best option. Remember that in the end it is expectation that drives markets. Whilst cryptocurrency seems to be here to stay, any particular coin is vulnerable to changing mood. The common perception that value always rises is self-evident falsehood, that is not the way Economics works. Currently everyone entering the cryptocurrency world is flying high on the belief that they will become millionaires. Of course they also think of those values in US Dollar terms, not in relative cryptocurrency terms.