Here are the differences,
The fglrx package, contains the driver version available at distro release.
The fglrx-updates package, contains the newest driver version packaged for Ubuntu.
The AMD website download, provides the newest driver released.
It takes time to properly package the official AMD releases, so fglrx-updates might not always be the absolute newest release. fglrx-updates is often still very recent, It was specifically packaged for Ubuntu, and I normally prefer it to the other options. The only time you would want to go either up, or down, is when a specific situation arises.
I've checked the packages that apt-get install would install for each of these. These aren't complete lists, but only list the differences from my Unity (ie., without any KDE programs) setup.
plasma-netbook and plasma-desktop differ only by whether they install the netbook or the desktop interface. kde-workspace is identical to plasma-desktop.
kde-plasma-desktop will install a few KDE programs: Dolphin, Konqueror, kde-baseapps, konsole, kwrite, and kde-passwd.
kde-standard installs a bunch of stuff on top of kde-desktop: Akregator, Ark, Dragonplayer, gnupg, Kaddressbook, Kate, KDE wallpapers, Kmail, etc.
kubuntu-desktop installs even more than kde-standard. kubuntu-desktop is the package you would download from the Ubuntu website if you wanted Kubuntu, but if you only want the Plasma interface, not any of the default programs, plasma-desktop might be sufficient.
Best Answer
Either one will almost certainly recognise your drivers.
If you want to have stability and long-term support choose 12.04. You can upgrade it to 14.04 next year if you want to - that will be an LTS as well.
13.10 is not a long-term support release. It is like a stepping stone on the way to 14.04.
LTS releases come every two years and they are always even numbered and released in April, hence the '04' bit. So 10.04, 12.04, 14.04, when it is released, are all LTS.
Other releases are more about introducing newer techniques and sub-systems into ubuntu as part of the development process.