All of them are all most the same, CentOS uses recycled code made available to them from Red Hat, but Red Hat is not officially affiliated with them. Fedora is fully sponsored by Red Hat and it has the 2nd largest community after Unbuntu. But both Unbuntu and Fedora are affiliated with actual companies, Canonical for Unbuntu and Red Hat for Fedora unlike CentOS, which helps with updates and error management. I personally prefer Unbuntu because the community is larger and with my experience I had great error help from the community and because Ubuntu offers several different distributions like Kunbuntu and Xubuntu. But Linus Torvalds, author of the Linux kernel, says he uses Fedora. But it really doesn't matter because they have very similar characteristics.
