When I installed my last distro, I made 3 partitions on my hard drive, one for the OS (about 8gigs), one for my home directory or folder (about 20gigs) and a swap space (about 1gig). So when the fever struck me to move back to Xubuntu on my 512mb laptop, there was no sweat. Sweat = complete re-setup tweaking. I told the Xubuntu installer to reformat the OS partition and make it bootable, then told it to make the old home partition the new home partition without formatting. All my files were intact along with my email and web browser settings and bookmarks. The only tweak was to get the wireless to work which requires two apps from the repositories via Synaptic.
Oh, why I moved back? Well I was living on the edge of not having enough resources to do graphics work. The Gnome, KDE and Unity desktops all have built in compositing and requires too much of my meager memory to run both the desktop and graphic/media apps too.
Below's a chart I snatched from a comparison page. Usability wise XFCE4 is lots leaner. Less desktop means more memory for your apps to run. I am thinking Fluxbox as an alternative but the leaner also means less built-in services and tools. If you know what they are, you can add them on your own.
|Desktop||Required RAM||Required CPU|
|Gnome 1.x||256||500 MHz|
|Gnome 2.x||384||800 MHz|
|KDE 3.x||512||1 GHz|