Show framework maturity: "Symfony compiles the container at build time so there is zero runtime resolution cost. Laravel resolves at runtime which is simpler but slightly slower."
Symfony uses a compiled container with explicit service definitions (YAML/XML/PHP attributes), autowiring by type-hint, and auto-configuration. Laravel uses a runtime container with simpler binding syntax, automatic resolution, and service providers. Strong answers discuss trade-offs: Symfony is more explicit and performant for large apps; Laravel is more convenient for rapid development. Best candidates have used both and can articulate when each approach shines.
Tests depth beyond surface-level framework usage. Candidates who only know one framework should still be able to discuss DI principles clearly. Red flag: confusion between service container and service locator pattern.