Thanks for being candid.
Well, let's turn that around. In the years from 1995 through 1998, Windows security was black magic both to defenders and attackers --- Win32 attacks didn't really mainstream until Solar Designer and Matt Conover broke the story on how to exploit overflows in the heap.
During the same time period, Unix systems --- and particularly SunOS/Solaris --- were positively riddled with trivially exploitable stack overflows. Number of Solaris worms and viruses during that time period? Zero.
I'm sort of digressing, but, can you come up with a logic that explains why OS X virus scarcity is about the intrinsic security of OS X and still describes the '90s?
I don't think malware prevalance has much to do with intrinsic OS security at all.
Also: smart not to lump OS X in with other Unixes. OS X has a very different, much more difficult challenge to deal with than server Linux.