1. 1. Scalability and Performance: Spring Boot is known for its scalability and performance. It uses lightweight and non-blocking architectures, allowing applications to handle a large number of concurrent requests efficiently. On the other hand, Symfony is not as lightweight as Spring Boot and may require additional configurations and optimizations to achieve similar scalability and performance levels.

2. 2. Language and Community: Spring Boot is primarily developed and supported by the Java community, which has a large and active user base. It benefits from the extensive Java ecosystem, including libraries, frameworks, and tooling. Symfony, on the other hand, is built on top of PHP, which also has a significant community but is not as extensive as Java's. The choice between the two depends on the expertise and preferences of the development team.

3. 3. Configuration and Convention over Configuration: Spring Boot follows the principle of convention over configuration, providing sensible defaults and reducing the need for explicit configurations. It enables developers to quickly bootstrap applications by automating common tasks. Symfony, on the other hand, leans towards explicit configuration, allowing developers to have full control over the application's behavior but requiring more manual setup and configuration.

4. 4. Dependency Injection: Spring Boot has a powerful dependency injection mechanism integrated into its core framework. It simplifies the management of object dependencies and promotes loose coupling. Symfony also utilizes dependency injection, but it requires additional configuration and setup to achieve similar functionality as Spring Boot.

5. 5. Templating and Frontend: Symfony has a built-in templating engine called Twig, which provides simplified syntax and powerful features for designing templates. It allows for reusable and maintainable code for frontend development. In contrast, Spring Boot does not come with a built-in templating engine, but it can integrate with various frontend technologies like Thymeleaf, FreeMarker, or React, depending on the developer's preference and requirements.

6. 6. Database Access and ORM: Spring Boot has robust support for database access through its Spring Data JPA module. It provides an easy-to-use and intuitive API for interacting with relational databases and offers support for various ORM (Object-Relational Mapping) frameworks like Hibernate. Symfony also supports database access through features like Doctrine ORM, but it requires additional configuration and setup compared to Spring Boot.

In Summary, Spring Boot and Symfony differ in terms of scalability and performance, language and community, configuration approaches, dependency injection mechanisms, templating and frontend options, and database access and ORM frameworks.