There is plenty of discussion of the merits of various Linux desktops these days. How does one go about loading, testing, and evaluating the options? One obvious solution is to load various distributions which have different desktops - this could mean different "spins" of one of the larger distributions (Ubuntu/Kubuntu/Xubuntu for example), or a completely different distribution for each desktop (Fedora for Gnome, openSuSE for KDE for example). But this takes time and disk space, and once it is all installed you have to reboot to change desktops.
An alternative solution would be to load a single distribution, and then add whatever desktops you would like to try out. Again, this can be tedious and time consuming if you have to find and load the core and all the bits and pieces for each one you want. It certainly can be done, and it might be the best way to go if you want to really learn and understand each one, and to end up with one that is really customized to suit your needs and taste.
If all you want, though, is to see how they compare in a very general way, there is a much simpler solution. Some distributions make it very easy to add a complete alternative desktop with a single selection. Two that I have been looking at today are Fedora 13 and Linux Mint 9. Both of those are best known for their Gnome distributions, and both have alternative "spins" for KDE, Xfce and Lxde, but it is not generally known how easily you can add another desktop to an installed Gnome base.
The Fedora base Gnome desktop looks like this:
In each of these examples, I have done very little of the adjustment or customization that I normally do to my desktops, so they are very close to the default after loading.
On Fedora, you go to System / Administration / Add/Remove Software. That starts the Gnome Package Manager, where you select "Package Collections", and then scroll down to find the desktop(s) you want - KDE Software Collection, Xfce Desktop and/or Lxde Desktop. You can select any or all of them, and then click Apply. Download and installation will take between 10 minutes and an hour, depending on how many of them you select and the speed of your internet connection.
Once the download and installation are complete, you simply Log Out. When the Login screen comes up again, select (or enter) your login name, and before entering your password you will see that there is a new option at the bottom of the screen - "Session". Click that, and you will get a list of the available desktops. Select one, and then go ahead and log in. It's that easy!
The KDE Desktop looks like this:
Poke around in the menus a bit, and you'll see one of the bigger side effects of adding desktops in this way. The different spins are always customized for whatever desktop they are using, and generally contain only the utilities and applications for that desktop. In this case you will see that there are lots of KDE and Gnome utilities mixed together in the menus.
Log Out again, and click Sessions again during Login. You'll see that it retains whetever the last session you used as the default for the next, it does not revert to Gnome (or whatever) each time. Click Xfce this time, and you'll get a desktop that looks like this:
This looks very much like the Gnome desktop, which is not surprising since it is based on GTK+. Poke around the menus and task bars a bit, though, and you'll see the differences both in appearance and performance.
Finally, log out again and click Sessions one more time. You'll have noticed by now that in addition to Lxde, there are also Openbox sessions listed. Openbox is the bases for Lxde, so when you chose Lxde for installation, Openbox came along at the same time. Choose Lxde, and you'll get a desktop that looks like this:
The first thing you are likely to notice about Lxde is how fast it is. Although Lxde is particularly well suited for older and slower hardware, it is gaining quite a following among those who prefer simplicity and speed.
Everything I have done here can also be done on Linux Mint 9, through the Software Center. Just select the desktop(s) you want and click install. The other distributions I looked at today (Ubuntu, openSuSE, Mandriva and Debian) didn's have such an obvious one-click desktop installation as these two. It is certainly possible that they do, and if anyone knows about it please feel free to post here to inform others.