I've been running Debian on a VPS for about two years and the ease of maintenance and overall sensible default security policies make it a great server OS. I'll always go for an OS where my default system is well-tested, stable, and trivial to maintain. I can then spend some time manually installing the latest versions of the two apps (web server and db) whose latest features I may need.

It seems to me that Ubuntu is pretty much like Debian with a more shorter upgrade cycle. Is that impression accurate? Also, does Ubuntu have any extra overhead that a Debian system might not have?