Ok yes Linux is free and I hate Mac for personal reasons but OS X is alot more secure than Linux, for one they don't really mod the code that much with Linux as they do with Mac operating systems ( Mac and Linux use the same source code of Unix). Linux don't have as much security because their operating system hasn't had as much attention as Mac has been able to put into their operating system and Linux's code has really diverged much from the normal source code.
In all OS X is a much better operating system than Linux and a safer one.