If something raising, they have more chances of reaching further while if something already falling, you will never know when it was the lowest point. Just a common sense for everything, not just crypto.
Each of us has our own point of view about when is the right time to start buying something in the market. When price rise quickly, there is usually a big chance to make a profit in a short time so that some trader will buy and sell again after reaching the profit target. Trader who usually buy when price go up never hold their asset for a long time when they make a profit and most of them are day trader.
About which one is the best in my opinion each of us has his own answer depending on the habit and opportunities that exist when trading.