1 Reason: LDAP. It's a key protocol that none of us can live without and it requires that authentication programs be compiled against OpenSSL.
Debian based systems compile against the GnuTLS libraries. Howard Chu (Chief Architect, OpenLDAP) noted, "GnuTLS considered harmful" and why.
http://goo.gl/jq9daYou can join AD with Debian systems but you should be aware of the inherent risks.
When you've vetted both veins of Linux (redhat and debian), the differences ultimately come down to this problem.
Debian holds the philosophical believe that all software included in its distro should be of a certain nature, licence-wise. And, in principal, I agree.
But Redhat holds a more pragmatic view. OpenSSL has been around forever. It's everywhere and unavoidable. Generally, when you login to a secure site, their secure certificate was issued with OpenSSL technology, as they have been since the late 90's. So Redhat leans heavily on OpenSSL and compiles all auth-mechanisms against it.
Test both systems side-by-side (redhat and debian), as I have, and realize that everything else will work out as you had envisioned it - everything, but the deal-breaker will be this 1 point. It's so frustrating.
For that reason alone, Fedora is now, and shall always be: King.
