Secure OS

Nowadays, probably the most secure OS are hardened Linux systems (like hardened gentoo and RHEL), Trustes Solaris 11, OpenBSD, QubesOS, Novell NetWare and OpenVMS.
What do you thing is doing the best security approach of this OS.
And what do you thing is better in practise?
(You can also include other OS you consider secure)
And what do you think os security on microkernel systems?

>>1
Linux
secure
/0

http://www.theregister.co.uk/2013/04/17/state_of_linux_2013/
each day some 10,519 lines of code are added to the Linux kernel, while another 6,782 lines are subtracted from it. All told, the kernel averages around 7.38 changes per hour – a phenomenal rate for any code base.
As of 2013, the Linux 3.10 release had 15,803,499 lines of code.

this just cant be secure.