1. Deployment Model: Azure SQL Managed Instance is a fully managed platform as a service (PaaS) offering, while Dimensigon is an open-source project that can be self-deployed on-premises or in any cloud environment.
2. Automated Backup and Patching: Azure SQL Managed Instance includes automated backup and patching services, whereas in Dimensigon, these tasks need to be manually configured and managed by the user.
3. Scalability: Azure SQL Managed Instance offers built-in scalability and the ability to automatically adjust resources based on workload demand, whereas scaling in Dimensigon may require more manual intervention and configuration.
4. Monitoring and Metrics: Azure SQL Managed Instance includes built-in monitoring and metrics tools for performance tuning and optimization, while Dimensigon may require third-party tools or custom configurations for the same functionality.
5. Cost: Azure SQL Managed Instance is a commercial service provided by Microsoft with associated costs, while Dimensigon is an open-source project that can be deployed at no additional cost, although deployment and maintenance costs may vary depending on the user's specific environment and needs.
6. Ecosystem Integration: Azure SQL Managed Instance seamlessly integrates with other Azure services and tools, providing a cohesive ecosystem for cloud-based applications, whereas Dimensigon's integration capabilities with external services may require additional development effort and customization.

In Summary, the key differences between Azure SQL Managed Instance and Dimensigon lie in their deployment model, automation features, scalability options, monitoring capabilities, cost structure, and ecosystem integration.