Hiring a FlexUnit developer is beneficial as they offer expertise in developing, testing, and debugging Flex applications. They ensure the application's robustness and reliability by implementing unit tests using FlexUnit. Their proficiency in this framework helps in catching bugs early in the development cycle, saving time and resources. Moreover, they can contribute towards seamless user experience by developing efficient and interactive UI components. FlexUnit developers also facilitate better team collaboration with their understanding of Agile methodologies and version control systems. Their technical skills combined with problem-solving abilities make them a valuable addition to any development team.