Both has unique advantage. Each trader maintain their unique style which suited themselves. There are many routes to making profit in crypto. Usually I'm doing both but l have reserved some coins as long term basis.
Yes, investments can be done considering both long term and short term. I have invested in ethereum, Neo, XRP and IOTA to hold on for a long time, whereas I have kept TRX, XVG,ADA,etc for short term profit. If you have enough time, you can do day trading as well as invest for the long term.
Also some amount must always be kept reserved in fiat currencies in order to buy cryptos low when they are in a massive dip. Thats sensible trading and also safe.