graeme_p - 6:45 am on Nov 20, 2012 (gmt 0)
I am not convinced MacOS is more secure because it is a BSD. Quite the opposite. The likes of FreeBSD are secure because they audit code - but so do the major Linux distros. From what I have read, Apple is less careful.
Linux also has very effective security mechanisms like Apparmor and SELinux, which distros integrate (so they work without the average user even knowing about them).
Mac OS also, until recently, lacked an integrated update system, and still does for the many apps installed from outside the store. Huge security drawback.
The lack of dependency management is also an issue, because any library not built into the OS needs to be separately updated by the authors of each application that uses it: on linux the distro just updates the library. It also means greater use of memory and disk space.