I've just been asking myself this question for a long time. It seems that at first we had SPA applications that sent all javascript on the client, and then SSR appeared, which generates on the server side. And that's the question that arose. What kind of rendering is more expensive for resources? SSR or SPA?
What is more expensive to the server? send all javascript on the client or generate some parts of the site on the server yourself, and then send it to the finished html. I understand that with the new PPR rendering, there is less overlap on the servers, because we have some static.
Just why does such a question arise in my head at all. For example, a person will want a website that does not understand this at all and you face the task of buying a server for your frontend. In theory, if you think logically, then you need a server for SSR more expensive than for SPA, because we have a website generation on the server. And thus the client will say: "well, why do I need this, it's also more expensive to buy a server." And the reel servers are not cheap