Openbsd vs. Hardened gentoo et al.

[m00tykins]

Which works better for security in the real world? Prevent-all-exploits-by-making-the-code-super-tidy (sel4, muon, coyotos/eros/capros, openBSD) or prevent-damage-after-the-exploit-occurs (hardened gentoo, qubes, selinux, minix 3)? Is it possible to do both?