I'm more a fan of centos, but have to give grudging respect to the
latest couple of versions of ubuntu server. Once you learn the new
way of doing things, it's quite easy to keep happy.
The version of Ubuntu Server I looked at one one of the first versions.
I am sure that Ubuntu has improved a lot since I looked at it. CentOS
Seems to me to be the best choice for a server right now. Why anybody
uses Fedora for a server I will never know but I see it all the time.
CentOS I think should get a lot more attention as a Distro than it
currently does.