And the Answer Is: The newer the better (sort of). That’s why FC is referred to as “bleeding edge”.
Packages spend some time in FC5 “testing” before they are released as FC5 updates.
If you go to any FC5 mirror and follow the path to “updates”, you will notice that one option is “testing”, where the “testing” versions may one day be released into FC5. You can use the “testing” rpms by enabling /etc/yum.repos.d /fedora-updates-testing-mirrorlist.repo.
But calling it “testing” is a little misleading. FC itself is a testing-type distro, similar to Debian Etch/testing. When you include “testing” in your update path, you move closer to Debian Sid/unstable.
RedHat has an article comparing Fedora and RHEL where they talk a little about stability vs. bleeding edge: http://www.redhat.com/magazine/019ma...fedora_rhel_1/