What are the best Linux distributions?

CentOS favours stability over being up-to date. For this reason it ships with packages that may be up to two years behind in order to ensure stability over everything else.

Using older versions for packages means that they have been thoroughly tested and used in production for quite some time, and are ensured to play well with each-other.

This strategy has paid off quite a lot in the past. One example is the Heartbleed bug which left CentOS unaffected since it was using a two-year old OpenSSL library which did not have the bug.