While Ubuntu Touch offers a unified experience across smartphones and tablets, Ubuntu for Android allows users to continue using Android on their smartphone and enhancing your experience when docked to offer a full Ubuntu desktop.
Canonical engineer Victor Palau demonstrates Ubuntu for Android running on a Google Nexus 4, which has been attached to an external monitor using a Slimport HDMI cable.
As you can see in the video, Ubuntu for Android offers a full Ubuntu desktop experience which even includes workspaces and the Ubuntu Software Center. However even the quad-core processor and 2GB of RAM on the Nexus 4 is far from capable of offering an optimal Ubuntu for Desktop experience.
This could be blamed on the fact that the Ubuntu for Android has not been optimized for the Nexus 4. But the fact that the Ubuntu Edge will have the fastest available processor and at least 4GB of RAM suggests that Ubuntu for Android is looking beyond current generation smartphones.
source - OMGUbuntu