Performance-wise - It literally doesn't make any difference.
The only real difference between a Debian based system, like Ubuntu - and a Red-hat based system, like CentOS - is the packaging format and the package management tools used to administer them.
If you prefer dealing with Red-hat/RPM based systems - go with CentOS. If you prefer working with Debian/deb based systems - go with Ubuntu (or pure Debian). Other than that - it makes no difference!