It's good for both, but it also has a very basic difference where if only one hand invests in Bitcoin, then the price fall that is too deep will happen to Bitcoin when someone sells all the Bitcoins he owns. But if a lot of people like small investors invest in Bitcoin according to their capabilities, then the potential for the Bitcoin price to fall will be slightly smaller, unless they (all small investors) sell Bitcoin simultaneously into the market. So Bitcoin will be stronger if held by many people than just one person.