Holding is better than selling in only some conditions and for only some people, those people who aren't knowledgeable enough to understand the market and its movements so that they can make effective trades, otherwise, one can earn more money with scalping and day trading than they can earn by holding because when you hold, you have to wait for years in most cases to get your desired profits but when trading, you get profit every day if you trade wisely.
Someone who can afford to do it should do both holding and trading because that will give them more profit eventually. They should buy and hold some Bitcoin and trade with the remaining funds that they have, this way, they will be earning profit from two sides which is great