When you hire a developer whose specialization is Magento you can be sure that a freelancer definitely has more than one project because working on one project is risky. It means that he cannot spend all working hours on your website. You’ll get required functionality later than you could.
While project is in the process, all tasks and changes are discussed with a developer who actually makes the code. It means that when you start a conversation with a freelancer the work stops. You lose your time as well as developer loses his.