With SSR, those round trips to the server could be down to single-digit milliseconds assuming your frontend server is in the same datacenter as your backend. Plus you send HTML that has actual content to be rendered right away.

A truly functional pageload can go from seconds to milliseconds, and you're transferring less data over the wire. Better all around at the expense of running a React Server instead of a static file host.

SSR can be a game-changer in domains like e-commerce. But completely useless for some other use case.

RSC advantages are a bit more complex to explain, because even a simple portfolio website would benefit from it. Contrary to the common belief created by long-term ReactJS dev, RSC simplifies a lot of the logic. Adapting existing code to RSC can be quite a mess and RSC is a big change of mindset for anybody used to ReactJS.