I feel like purchasing a token before the listing gives much more space for profit, but he mentioned that there's also a huge risk of not knowing whether it will end up getting listed and that was a fair point. He also raised the point that buying tokens after their listing was safer, but even if it's true that it holds less profit potential than the former, it also has huge potential if it gets listed on a top exchange.
Neither is better than the other, both have their own risks & profit opportunities, for example, tokens that are not yet listed on CEX, do have a higher profit level if the token is later listed on CEX. Likewise, if the token is already listed on CEX, it means that CEX considers the token to be a safe token, and we will definitely only have a smaller chance of making a big profit.