Lubuntu vs Xubuntu
Xubuntu and Lubuntu are alternative distributions for Ubuntu, based on XFCE and LXDE desktop environments respectively.
Both were designed to be "lightweight" distributions and can work on machines with just 256 MB of RAM. Performance on netbooks and relatively slow computers is good. Both desktop environments provide adequate tools for everyday use without having the user resort to manual editing of configuration files.
The more mature and feature-rich desktop systems typically provide more a comprehensive set of configuration tools, while consuming more memory and taking longer to start. Along these lines, XFCE is lighter than the Gnome Desktop Environment. LXDE is even lighter than XFCE, while further slimming down on features.
Newer versions tend to need more RAM: while Lubuntu 12.04 was ok with 256 MB on desktop, it is recommended to have 384 MB with the 14.04 LTS . Similarly, the 64 bits editions need more RAM than the 32 bits editions, so 64bits CPU with low RAM should get either more RAM or stick with the 32 bits edition.
|Resource||Lubuntu: LXDE   ||Xubuntu: XFCE |
|Minimum RAM to run without desktop||50-60 MB||192 MB|
|Minimum RAM to run desktop||224 MB||512 MB|
|Recommended minimum RAM to run||384 MB||512 MB|
|RAM to install||160 MB||256 MB|
|RAM to install with Alternate CD (text mode)||64 MB||64 MB|
XFCE recommends 512 MB of RAM for optimal performance and needs at least 256. The alternate install CD can make do with just 64 MB of RAM . Lubuntu is further lighter than Xubuntu. Phoronix benchmarked LXDE, XFCE, Gnome & KDE and found that LXDE was the lightest of them all, followed by XFCE. Linux magazine reviewed Lubuntu and found it using just half the RAM when compared to XFCE.
XFCE seems to be stable right now while LXDE is in active development and is being ported from GTK2 to Qt.