So what are the differences between these Siamese twins? Looking at installation, the desktop, package management, and community in the two distributions what emerges is not so much major differences as differences of emphasis, and ultimately, of philosophy. More here

In the end, the difference between the Debian and Ubuntu communities lies in their core values. Although less important than a few years ago, Debian remains a community-based distribution, dedicated to its own concepts of software freedom and meritocratic democracy, even at the expense of rapid decision making. Ubuntu, however, for all its strong community, is also the key to Canonical’s success as a business. If Ubuntu is more hierarchical than Debian, it is still more open than the majority of high-tech companies.