Why do SEOs prefer server-side rendering?

Server-side rendering can be a bit faster at the initial request, quite simply because it doesn’t require as many round trips to the server. JavaScript requires the search engine to spend longer rendering, which means additional electricity expended, increased CPU demand, as well as dramatically slowing down the standard rendering process. For server-side rendering, all of the HTML content is present in the source code. This lets search engines request, crawl and index it immediately, resulting in improved page speed performance (a major ranking factor), and all impactful content being indexed and cached. This consistently leads to improved ranking in search results.