like you say, the benefit is to easily attach styles to components (in the same programming language, compared to scss/css modules)

note: @emotion/styled is equivalent to styled-components, lighter and easier to set up for SSR (it works out of the box https://emotion.sh/docs/ssr#default-approach)

When using server-side rendered pages, there's no performance loss on the client-side, maybe a little more processing server-side, not sure if significant