1. Architecture: Ada is a statically typed language designed for high integrity systems, with a strong emphasis on safety and security. On the other hand, Elixir is a dynamic, functional language built for scalability and fault-tolerance, ideal for building distributed systems.
2. Concurrency: Ada provides tasking for concurrency, allowing developers to create multiple concurrent tasks that can communicate through shared data structures. Elixir, however, utilizes lightweight processes that communicate via message passing, making it easier to build highly concurrent and fault-tolerant systems.
3. Syntax: Ada follows a more traditional syntax similar to languages like C/C++, with strict rules and a focus on readability and maintainability. Elixir, inspired by Erlang, has a syntax that is more concise and expressive, making it easier to write and understand complex code.
4. Type System: Ada has a strong, static type system that enforces strict type checking at compile time, helping to catch errors early in the development process. Elixir, being dynamically typed, allows for more flexibility but may lead to runtime errors if types are not handled correctly.
5. Error Handling: Ada has built-in support for exceptions and a robust mechanism for error handling, enabling developers to write reliable code with proper handling of exceptional situations. Elixir takes a different approach with a "let it crash" philosophy, allowing errors to bubble up and be managed at a higher level, promoting fault-tolerance in distributed systems.
6. Community and Ecosystem: Ada has a smaller community and ecosystem compared to Elixir, which benefits from a vibrant open-source community and a rich ecosystem of libraries and tools that make it easier to develop and deploy applications.

In Summary, Ada and Elixir differ in their architecture, concurrency model, syntax, type system, error handling approach, and community ecosystem, catering to different needs in software development.