Lubuntu 12.04 is NOT an LTS.
I think you should stick with Ubuntu, perhaps Xubuntu (Xfce). The difference is in the default apps, Desktop interface and the consumption of resources.
Originally Posted by https://wiki.ubuntu.com/Lubuntu
What you can do?
Install Ubuntu 12.04
Then Install Xfce, so you have both Unity, and Xfce. You can choose which one you want from Login box (right-hand top gear icon will help you choose which).
To install just Xfce check out the Screenshots to know the difference
sudo apt-get install xfce4
Install the whole Xubuntu-desktop (this comes with all the default applications), you might end up using two similar applications one from Ubuntu and one from Xubuntu. For instance, you will have two file-browsers, Nautilus from Ubuntu and Thunar from Xubuntu.
sudo apt-get install xubuntu-desktop