1. Server-Side vs. Client-Side: Express is a server-side framework used for building APIs and web applications, while LitElement is a client-side library for building web components.
2. Language Compatibility: Express is used with Node.js and JavaScript on the server side, whereas LitElement is used with HTML, CSS, and JavaScript on the client side.
3. Routing: Express uses routing to handle requests and define endpoints on the server, while LitElement does not handle routing directly but can be used in conjunction with other client-side routers or frameworks.
4. Component-Based Architecture: LitElement promotes a component-based architecture for building reusable web components, whereas Express focuses on structuring applications using middleware and route handlers.
5. Template Rendering: Express allows for server-side rendering of templates using engines like EJS or Pug, while LitElement focuses on client-side rendering and updates using the Shadow DOM and reactive data binding.
6. Data Handling: Express is commonly used to handle data processing and manipulation on the server side, while LitElement is focused on user interface logic and interactions on the client side.

In Summary, Express and LitElement differ in their server-side vs. client-side nature, language compatibility, routing capabilities, component-based architecture, template rendering, and data handling approaches.