We know that holding Bitcoin is better when users have full control over their funds. What makes an open source software better? Is there any advantage on using it than using close source wallet.
The software can be always tricked, i mean if we talk about wallets, if you go with a close source wallet provider what warrants you that he isn't saving a copy of your privatekeys in their DB... Another problem about closed source project is the security, you can't know if your provider is hashing passwords before saving them, and other security stuff. But with open source projects this doesn't happen because since users have access to the code, users can be sure if the provider is saving our information, and if he is managing security by the right way.
In other words, if bitcoin were a closed source project it would never have success because no one would trust on the project.