> If the API calls can be limited to one call per user action/page visit, the experience would be better because only some API data has to be transferred instea

> If the API calls can be limited to one call per user action/page visit, the experience would be better because only some API data has to be transferred instead of an entire HTML page HTML pages are not that big, though, unless you put a lot of content around the data. Not to mention JSON can be wasteful, and contain more data than needed. And lots of SPAs require multiple roundtrips for fetching data. And even if you do have lots of content around your data, there are alternatives, like PJAX/Turbolinks that allow you to only fetch only partial content, while still using minimal JS compared to a regular JS framework.