You can install multiple desktop environments in the same Ubuntu system, by installing the corresponding package. Most of these are metapackages.
- GNOME 3 with Unity / Unity 2D:
ubuntu-desktop
- GNOME 3 with GNOME Shell:
gnome-shell
- GNOME 3 with GNOME Fallback (looks like, but isn't, GNOME 2):
gnome-session-fallback
- KDE 4 Plasma Workspaces -
kubuntu-desktop
- Xfce 4 -
xubuntu-desktop
- LXDE -
lubuntu-desktop
That's not an exhaustive list of metapackages providing desktop environments. Other variants, like edubuntu-desktop, can also be installed this way.
The best way to have an Ubuntu system with GNOME Unity, KDE 4, and Xfce 4 installed is probably to install the Ubuntu desktop CD, then add the kubuntu-desktop and xubuntu-desktop packages.
If you're installing from the command-line with sudo apt-get install ..., make sure to run sudo apt-get update first to update information about what versions are available of software to install. Otherwise, and especially given that these are big metapackages:
- It may try to install some versions that are no longer available, causing the installation to fail.
- It may try to install some versions that are buggy and don't work right with each other.
- You may incur security vulnerabilities (though you could fix them by a subsequent upgrade of everything to the latest version).
- It takes much more time and effort to upgrade potentially hundreds of packages after installing old versions, than to run
sudo apt-get update first and install the newest recommended versions in the first place.
Remember, when you install these big metapackages, many packages are installed.
Of course, you can install them just as well through the Software Center (no sudo apt-get update needed, it's taken care of automatically).
If you have more than one desktop environment installed, you can work in one system where you have access to everything. This is quite valuable, so this is probably what you'll want to do. However, note that, unless you do quite a bit of manual reconfiguration, you'll see all applications when in each desktop environment (in its menus, or when you search for installed apps), including applications designed for the other desktop environments.
They will still run, and most of them without any problems at all, since even those applications that are very strongly pinned to a particular DE have that DE installed in this scenario. When running, though, they may cause significant background user services associated with their desktop environment to start up in the background. This sort of thing is particularly common when running KDE programs in GNOME.
Best Answer
To simply answer your question, yes, all flavors can run all programs. There are a lot of choices for types of Ubuntu you want. Each one provides a different purpose for the user. These can be seen on the official page for the different flavors:
After reading through this and possibly on some community recommendations, you can tell which one is for you. The difference besides style and pre-installed (note the difference between what it can run and what it comes with) programs is only noted in two official flavors:
Both of these flavors are more optimized for less intensive resource consumption. Although, they do have the same potential as the other flavors. Hope this answer helped you with deciding which one you should get.