Both is important but to if I will select very correctly I wouldn't mind to choose holding, in holding you don't have to be afraid of the risk of losing your coin or tokens. The only thing there is for to target your investment period and work towards it like to be patient while bitcoin price keep soaring, but since you made mention of trading well, you can try it out to see how it works but I must tell you the truth you need to study hard to understand how the trading works and to keep you earning. The important thing is that you can't just begin to make money from trading if you don't fully understand how the system works currently and it's something you have to study a day or weeks before jumping into trading, let say it would take years or as long as can comfortably trade and make profits from it without incurring much lost.
That depends on the token or coin you are holding. Some tokens are best to hold short term and then sell-off once it is increasing in the market. The dilemma usually is - can the project survive? Or is it only for the sake of the devs' pockets? Because if it is the latter, we all know that you will be screwed if you sell your coins late. As we can see, very few can survive as most of them have no real use case in the market. They are just driven by hype for the devs to gain profits. Afterwards, they will slow down up until they will totally abandon the project.