Pros

• A very active development community
• Well-known and considered easy to use
• Very large software repositories (and all the benefits of Debian, on which it is based)
• A predictable release schedule and the latest software
• Update notifier

Cons

• A full version of Ubuntu can take up over 4GB

Download link: https://help.ubuntu.com/community/Installation/MinimalCD.

This guide will lead you through the installation and tell you how to get a barebones installation with essentially only an X Window Manager, Login Manager, and Synaptic.

Follow the instructions here for performing a minimal install of Ubuntu and installing Xubuntu-desktop. The guide implies that the full installation of Xubuntu is about 1.2GB (and states that it is less than 1.5GB).