these two strategies are not separate from each other so you don't exactly need to only choose one for your trading strategies. you can do both and also remember that different markets require different type of approach.
for example you can do day trading in both altcoin and bitcoin market but long term investment only works with bitcoin and not a single altcoin is good for that.
However, if you look for long term trade, technique that I used is I buy at dip and keep it longer, it gives me success doing it, just be patient to wait.