This is a statics from Linode
56% of deployments are Ubuntu
21% of deployments are Debian
17% of deployments are CentOS
2.2% of deployments are Fedora
1.8% of deployments are Arch
with more than 50% using Ubuntu and more than 77% if you combine it's upstream Debian. It looks like Debian family gain traction over Red Hat. So, what's your client's distro choice?