Css-in-JS Pros: - Enforce only local styles - Developer productivity - Better theming support - Better support for dynamic styles - Easier to consume

Css-in-JS Pros: - Enforce only local styles - Developer productivity - Better theming support - Better support for dynamic styles - Easier to consume packages - Typesafe styles Cons: - Worse runtime performance - Bigger bundle size - Fragmentation of ecosystem - Idiosyncratic additions to css It depend on your project. For small and medium sized projects I would recommend CSS-in-js. For large and performance-sensitive css-modules would be better.