cran.r-project.org runs on a single old-school server in Austria
and could potentially be overloaded if "everyone" used it.
cloud.r-project.org is a cloud-based repository that "automatic redirection to servers worldwide [...]", cf. https://cran.r-project.org/mirrors.html.
I assume, that cloud.* can be scale up as needed. Out of the official CRAN mirror, this should be the safest one to pick if a static CRAN mirror is needed.
4f297f4336