Debian or Ubuntu?

[Kitchen]

I've been lurking on the list for a while, but haven't posted before. 
We're looking at upgrading our co-lo web server which is now running 
Debian Sarge. Some people we know have suggested we take a look at 
Ubuntu, which is based on Debian. Is there anywhere a balanced 
overview of the pros and cons of using Debian or Ubuntu?

I'd appreciate any URLs or your own thoughts. Thanks.