There are two main benefits to server-side rendering: - time to first paint is faster on CPU-constrained devices (e.g. low-end phones), and - interoperability

There are two main benefits to server-side rendering: - time to first paint is faster on CPU-constrained devices (e.g. low-end phones), and - interoperability with non-JS-powered UAs (like robots) I believe a big part of the desire for server-side rendering is a fear that search performance may be penalized if a crawler doesn't speak JavaScript, or tries to crawl the page when it's not in a state a human user would consider stable. I know there's been work done on Googlebot to make it correctly interpret client-rendered pages. If you could confidently say "Using Web Components will not have a negative affect on your search ranking; Googlebot can crawl and understand Web Components at least as well as traditional HTML elements," it would allay many of the concerns about WC, especially with regard to server-side rendering.