I do believe we do must do both, because at crypto world, having some coin might mean we will get a bigger value, with saving, with investment we can grow our bitcoins fast as well risk to loose them.
Since we are in crypto world and bitcoin is the best crypto to save. If you are going to keep on saving you are just like investing into it already.
Because of holding it, you are also investing because you are waiting for the right time to sell your bitcoins and as well as your time is being invested.
And that is what we called 'trading', holding is trading.