I think it's better to hold coins that have good prospects than to hold pesky coins because we don't need to worry when the cryptocurrency market suddenly goes down, but it all depends on each of our choices.
Identifu=ing coins that have good prospects, apart from the top 10 or 20 coins on CMC might be a problem. There are some coins that might appear to be good at first, but in the long run, they still fail. Those who hold such coins for a long period tend to lose their investment. Therefore, the best might've to go for the top coins, for long term investment, except you are ready to take some risks.