Centos certainly is the most popular, and we run it on 99% of our servers. However, you have some real followers of the Debian and Ubuntu flavors of linux for stability and security reasons. I can't say from experience it is any better, it is just what you prefer. But if you are running a control panel that handles everything, it really won't make much difference other than how you perform many options at the command line.
CentOS is our preffered option for dedicated web servers, especially with cPanel.