|As informative as this may be, this is missing one thing.
Debian is not Linux. It runs on top of Linux, but can also run on top of HURD, and soon enough will be supported on top of a BSD kernel.
Of course the more integrated OpenBSD currently is more secure because it is more stable (hold on), that is not the end of the story. It is stable in that the foundations have not been changing very significantly… the code audits tend to reinforce previous structure, not introduce new uncertainties. With well supported hardware, this will make the system more stable (as in robust, non crashing).
While OpenBSD will remain highly secure in its default configuration, in practice Debian will surpass OpenBSD eventually. As Debian tools become more widely used and platform independant, they will be forced to become more robust to deal with the variety of systems they handle. The always changing Linux kernel will be the weakest link as the Debian system stabilizes in spite of Linux.
At this point, you will choose from the best of both worlds. Run a robust and dynamic Debian system on a stable, well defined kernel like OpenBSDs. Mua-ha-ha-ha!!!