Debian vs CentOS
When it comes to setup web servers, or Internet servers (web, email and ftp) there is usually two GNU/Linux distributions that comes to mind, Debian and CentOS. Some people are starting to use Ubuntu server, but let’s focus on CentOS and Debian, as Ubuntu is a Debian derivative.
I think you should consider two main points when choosing a web server.
Easy of upgrades
CentOS is a community driven clone of Red Had Enterprise Linux. This should make it very, very stable and suitable to be used as web server. In fact by the time of this writing CentOS is the second most used distribution for web servers, according to Wikipedia.