Which should I choose?

The main idea for choosing SSR vs CSR vs Server or Client side data fetching is to pick the pattern that works the best for your usecase.

Either way you go, Server side or Client side, as long as you cache the data correctly you should end up with a fast app.

If you can use HTTP Streaming, server side data fetchs seem to be the way to go, with some client side fetching and caching to speed up some common page transitions.

Without http streaming, it makes more sense to fetch all the quick stuff on the server, then save any long poll / below the fold content for client side fetching once the page renders. You'll have to take it on a case by case basis when designing the app.