SSR is only easy if your frontend is written exclusively in SSR-compatible libraries and your backend is node.js, and even then you need to adjust your frontend code for SSR because node.js doesn't have all the browser APIs that your code could be using (like XHR or the real (not virtual) DOM).

On the other hand, puppeteer executes your application in virtually the same environment as the user's browser, without polluting your frontend architecture with SSR concepts and limitations.

Yes, you'll need to set up a bit of infra initially. Depending on the use case it may very well pay off.