It's typical to select the repository that is closest to your geographical location. Alternatively, you can run Repo Speed Test and select the repository that gives you the fastest speed. Of course, it's uncommon to get a connection faster than that of the PASS server, which you get access to after making a donation to help keep PCLinuxOS going.
Whatever you do, DO NOT enable more than one repository at a time (excluding the special games repo, which can be activated with any other selected repo).
HTH!
parnote