Diversification is important with investing. People have made a lot of money investing in bitcoin and alt coins due to it's volatility, same can be said about the stock market. The general rule of thumb is only invest as much as your willing to loose. Diversify as much as you can for example theres cash, stock's, mining, bitcoin, alt coins, P2P lending, there's so many great options out there. It all depends on your risk appetite and how easy it is to get into these investment opportunities.
So to answer your question, both and add a couple more options in there for diversification.