Hiring a Grails developer offers numerous advantages, especially for web application development. Grails is a powerful, Groovy-based web application framework that provides a highly productive environment through convention-over-configuration, sensible defaults, and opinionated APIs. This leads to a significant reduction in development time, as developers don't have to spend unnecessary hours on boilerplate code.

Grails developers can leverage the robustness of the Spring Boot framework, upon which Grails is built, ensuring a solid foundation for your application. They can seamlessly integrate Java libraries, making it versatile and adaptable to existing technologies.

Moreover, Grails supports domain-specific languages (DSLs), which simplifies the task of coding complex applications. The framework also promotes clean code architecture and maintains readability, which is beneficial for team collaboration and future code maintenance.

Grails developers can also easily create robust unit tests due to Grails' seamless integration with testing frameworks like Spock. This ensures the delivery of high-quality, bug-free code.

Finally, the thriving and active community around Grails provides excellent support and continuous updates, which can be crucial for keeping your application current and secure. Hiring a Grails developer, therefore, offers you the opportunity to create dynamic, scalable, and maintainable web applications.