The argument I'd bring up would be about risk, What he is doing is a fundamentally more risky strategy. If you keep the bitcoin you know you'll have that amount of bitcoin as long as you don't lose the keys , get hacked etc. What you're not exposed to is price risk. What he is doing may get him more bitcoin in the end, or less. We don't know. He does not know. If he is okay with that, fine. But that's the argument: the lack of certainty.