What is the difference between Ubuntu, Kubuntu, Xubuntu and Lubuntu restricted extras/addons?

While I use Lubuntu, for example, do I need ubuntu-restricted? or those of xubuntu or kubuntu? Do they add some enhancement, like supplementary media codecs, to what I have in lubuntu-restricted?

apt-cache search --names-only ".*ubuntu-restricted-(addons|extras)"
kubuntu-restricted-addons - Commonly used restricted packages for Kubuntu
kubuntu-restricted-extras - Commonly used restricted packages for Kubuntu
lubuntu-restricted-addons - Commonly used restricted packages for Lubuntu
lubuntu-restricted-extras - Commonly used restricted packages for Lubuntu
ubuntu-restricted-addons - Commonly used restricted packages for Ubuntu
ubuntu-restricted-extras - Commonly used restricted packages for Ubuntu
xubuntu-restricted-addons - Commonly used restricted packages for Xubuntu
xubuntu-restricted-extras - Commonly used restricted packages for Xubuntu

-addons vs -extras

Looking at the packages it's easy to tell these are metapackages - they're just depending on other packages and are empty by themselves. The only reason for their existence is to ease the user in installing a set of packages by just setting dependencies.

By looking at the dependencies of these you can see that -extras is depending on -addons, thus making the former an extension on the latter.

The description of both packages (apt-cache show ubuntu-restricted-addons):

Commonly used restricted packages for Ubuntu

This package depends on some commonly used packages in the Ubuntu universe and multiverse repositories.

You should not install this package directly, but instead install the ubuntu-restricted-extras package.

apt-cache show ubuntu-restricted-extras:

Commonly used restricted packages for Ubuntu

This package depends on some commonly used packages in the Ubuntu multiverse repository.

Installing this package will pull in support for MP3 playback and decoding, support for various other audio formats (GStreamer plugins), Microsoft fonts, Flash plugin, LAME (to create compressed audio files), and DVD playback.

Please note that this does not install libdvdcss2, and will not let you play encrypted DVDs. For more information, see https://help.ubuntu.com/community/RestrictedFormats/PlayingDVDs

Please also note that packages from multiverse are restricted by copyright or legal issues in some countries. See http://www.ubuntu.com/ubuntu/licensing for more information.

Now that mystery is solved, let's see what the differences are on the Ubuntu derivative part.

ubuntu- vs kubuntu- vs lubuntu- vs xubuntu-

This just depends on what the derivatives have decided on to ship and recommend. Sometimes this includes Desktop Environment specific packages. Some examples:

• The dependency on libk3b6-extracodecs in kubuntu-restricted-addons is only valid for KDE as this package is for K3b (KDE disc burning application) only.
• The lubuntu set appears to contain a lot less dependencies and especially excluding the gstreamer codecs. This may indicate that LXDE's default player is not GStreamer based, and it's sane not to install all kinds of GStreamer libraries probably not being used in a Lubuntu installation.