Both are good in their own way. It will just depends on the attitude of a person. If you are a person that doesn't want to work from time to time, holding is the best for you especially if you are holding decent amount. Now if you want to rake a risk and make a much faster profit, then go trading especially if you're a non-busy person. You can focus so much in trading.
Yeah I think you will increase your gains by doing both with different coins. I have a sort of investment which i only have for short term trading and i make a good earning through it. Coins with higher market cap are changing slowly so one can easily keep track of them and trade them more frequently. But with smaller coins It is better to hold them because they often have potential of very high return in short period of time.