1. Language and Technology Stack: ASP.NET is a framework developed by Microsoft and primarily uses C# as its programming language. It has a wide range of features and libraries built into the framework, making it more suitable for enterprise-level applications. On the other hand, MEAN (MongoDB, Express.js, AngularJS, Node.js) is a full-stack JavaScript framework that uses JavaScript for both frontend and backend development. MEAN is more lightweight and flexible, making it a good choice for smaller, more agile projects.

2. Database: In ASP.NET, Microsoft SQL Server is the default choice for database management, offering robust features and strong performance. However, developers can also use other databases like MySQL or PostgreSQL. In contrast, MEAN uses MongoDB, a NoSQL database, by default. MongoDB is known for its scalability and flexibility, and it allows developers to easily work with JSON-like documents. This difference in database technology can influence the design and scalability of the application.

3. Community and Resources: ASP.NET has been around for a long time and has a large and active community. It has a vast number of resources, including tutorials, documentation, and libraries, available for developers. This extensive community support makes troubleshooting and finding solutions easier. On the other hand, MEAN is a relatively newer framework, and its community is still growing. While it has a decent amount of resources available, it may not have the same level of community support as ASP.NET.

4. Scalability and Performance: ASP.NET is designed to handle large, enterprise-level applications and can easily handle high loads and traffic. It provides built-in support for high-level scalability and can efficiently handle thousands of concurrent requests. MEAN, although not as powerful as ASP.NET in terms of scalability, is still capable of handling moderate loads effectively. It is well-suited for smaller to medium-sized applications that don't require extensive scalability.

5. Integration with Microsoft Products: ASP.NET is tightly integrated with other Microsoft products like Azure, Visual Studio, and SQL Server. This integration makes it easier to develop, deploy, and manage applications within the Microsoft ecosystem. MEAN, being an open-source framework, does not have the same level of integration with Microsoft products, which may not be ideal for developers who heavily rely on Microsoft technologies.

In Summary, the key differences between ASP.NET and MEAN lie in their language and technology stack, choice of database, community support, scalability, performance, and integration with Microsoft products.