PostgreSQL is a robust and versatile database management system that offers advanced features like custom data types and efficient write operations, making it ideal for complex and large-scale applications such as e-commerce platforms and financial systems. MySQL, on the other hand, is known for its simplicity and efficiency, catering well to more straightforward, static systems where speed and ease of use are essential. The choice between PostgreSQL and MySQL ultimately depends on the project's specific scale and operational intricacy needs, with PostgreSQL being a better fit for projects that demand the handling of voluminous or complex data.