I agree with QatQat that Debian is probably more sensible out of the box. However, Redhat has made considerable strides in their default configurations.
You could optionally add selinux as an overlay to your linux box and become factors more secure. And factors more annoyed.
Frankly, the distros out today probably represent very few of the real security issues you'll face. Kernel vulns are often hard to exploit without local access.
More likely, you'll see vulns from:
-- poor or late adoption of package upgrades for applications
-- poor coding practices for web-facing sites using loosely structured languages like PHP
-- leaving un-needed services and user accounts on the machines
-- poor password generation and expiration practices
-- SQL injection
-- untested F/OSS applications/web code
-- running services with unnecessary levels of privilege
-- stupid user tricks
These are all activities/responsibilities that a system administrator and a good security policy document must address. Your distribution may have a default position on some of the settings or enforcement, but ultimately security is an ongoing activity and does not come out of a box. Remember, new methods to exploit you are always under development.
D.E.R. Management - IT Project Management Consulting