1. Server-side rendering: Blueprint is primarily a design system used for UI components, whereas Sapper, a framework based on Svelte, enables server-side rendering. This means that Sapper has the ability to pre-render pages on the server, leading to faster initial load times and improved SEO.
2. Data fetching: Sapper provides built-in support for fetching data during the server-side rendering process, making it easier to handle data requirements for different routes. In contrast, Blueprint focuses more on the presentation layer and doesn't offer specific features for data fetching.
3. Client-side hydration: Sapper includes capabilities for client-side hydration, allowing the server-rendered content to be re-hydrated on the client-side for interactive components. Blueprint, being a design system, does not have this functionality as it focuses on defining UI components.
4. Static site generation: Sapper can generate static sites, providing a way to pre-build and optimize the website for performance and scalability. Blueprint is not meant for static site generation and is more suited for building interactive user interfaces.
5. Routing: Sapper offers a file-based routing system, where routes are automatically generated based on the file structure, simplifying the organization of pages. Blueprint, on the other hand, does not handle routing as it is not a framework but a design system for building consistent user interfaces.
6. Ease of use: Sapper, being a framework, provides a more streamlined development experience with integrated features, whereas Blueprint requires additional setup and customization to be integrated into a project due to its focus on design elements.

In Summary, Sapper (Svelte) distinguishes itself from Blueprint by offering server-side rendering, built-in data fetching, client-side hydration, static site generation, file-based routing, and a more streamlined development experience compared to Blueprint.