1. Templating: Aurelia uses a powerful and flexible templating system that allows for two-way data binding and seamless integration with custom elements, while Backbone.js relies on underscore.js templates for rendering data.

2. Routing: Aurelia provides a built-in routing system with support for nested routes, route lifecycle events, and lazy loading, while Backbone.js requires additional libraries like Backbone.Router for routing functionality.

3. Data Binding: Aurelia features a more advanced and automatic data binding mechanism that updates the UI whenever a bound model changes, eliminating the need for manual DOM manipulation. Backbone.js, on the other hand, requires more explicit data binding through event handling.

4. Dependency Injection: Aurelia has a built-in dependency injection container that allows for easy separation of concerns and facilitates unit testing, while Backbone.js does not have a native dependency injection system.

5. Component Architecture: Aurelia promotes a modular and component-based architecture through its support for custom elements and view models, making it easier to build and maintain complex applications. Backbone.js, while allowing for modular components, does not have the same level of built-in support for custom elements.

6. ES6/ES2015 Support: Aurelia is designed with ES6/ES2015 in mind, making use of modern JavaScript features like classes, modules, and arrow functions, which can lead to cleaner and more concise code. Backbone.js, while compatible with ES6, does not take full advantage of its features.

In Summary, Aurelia and Backbone.js differ in templating, routing, data binding, dependency injection, component architecture, and ES6 support.