Oh good god!
This thread is painful!! Right, here we go, sorry if it's too much truth at once but:
* Windows has its insecurities, its advantages and its disadvantages
* Mac OS X has its insecurities, its advantages and its disadvantages
* Linux (*all* distros) has its insecurities, its advantages and its disadvantages.
Now can we all stop being win/mac/lin-tards and just see the bigger picture - security is important for every OS, no OS is above patching security flaws, implementing the latest security techniques and requiring AV software. Every machine, at some stage, is going to be targeted by some sort of malicious attack regardless of the OS its running. Some are harder to crack than others but lets face it - hackers love a challenge!
I'm sure some are wondering which OS this prophet of truth uses - I use linux at both work and home (fedora and AIX at work, and I used to use fedora at home but got a dell netbook so am stuck with ubuntu NR for a while).