Regardless of which side you're on (though as a true computing enthusiast, you shouldn't be taking sides), you've heard the arguments back and forth on the which operating system is truly safer – Mac OS X or Windows. [more]
All this time everyone has been saying Macs are more secure.....
I guess you have to look at the definition of: 'what is secure'
If all hacker eyes are pointing to windows and nobody takes a look at 'the other product' it would look like windows would be more insecure as there will be found many more problems. But by no means it says anything about other products being safer as looking to the code, although some may argue that their product is safer as its less under attack.
In the end all products are made by human; and often based on the same ideas (functionality) and thus equally vulnerable.
Just as with farming; it is a good idea to have a mix of different products.