Interesting discussion on experiences using Centos/Redhat, Ubuntu, and Debian. Funny nobody mentions OpenSuSe, Gentoo, or Arch on any serious server deployment. Summary of the discussion.
1. Centos/Redhat. High-performance computing (HPC), scientific stuff, Oracle databases, or Java-related stuff.
2. Ubuntu. Mostly desktop. Latest and greatest stuff. The (Long Term Support) LTS is crappy for HPC.
3. Debian. Server stuff or a more stable and conservative Ubuntu (LTS).
To be fair, for typical LAMP-stack server, all above mentioned GNU/Linux distros are good enough. But Ubuntu/Debian are far more convenient to get more latest greatest packages.