Note that MPAs can also opt-in to prerendering, where the browser spins up a hidden background tab (sort of) that renders the next page, and then gets activated when the user clicks a link. This gives truly instant-feeling navigations. More detail at https://developer.chrome.com/blog/prerender-pages/ . For now page-to-page prerendering is Chrome only, but since it's a progressive enhancement that seems fine. (Safari does prerendering from the URL bar as well.)

SPAs can get this sort of thing too, but it's less automatic and generally requires framework support for keeping track of chunks of not-yet-visible, non-user-interactable inert DOM and matching them up with link clicks. Whereas with MPAs, because you're using the standard page rendering and link paradigm, the browser can manage for you.

Source: engineer on Chrome working on this feature :)