They're both vulnerable. Therefore the author shouldn't criticize Windows for being more vulnerable than Mac, when the Macs he promotes are just as, if not more, vulnerable.
macs are a smaller target. Having more vulnerability in one OS or another is way less a factor vs how many potential target exist for one OS vs another. If a cracker/criminal decides to mass infect, they will choose the bigger "market".
If you are targeted by an individual/funded organization, it doesn't matter which OS you use, because there just needs to be one vuln and you are own'ed.
Therefore, it makes sense to use an OS that has a smaller marketshare. That keeps you safer than anything else.
By that account it is better to use obscure Linux as it is usually harder to find 1 exploit that works on all the distributions, and by that account it would be best to write your own OS.
But in real world, Windows are good enough for a lot of stuff and specifically gaming and office. If kept up2date will be secure enough.
I think talking about security superficially is not really valuable.
Sorry I don't know much about Mac update schedules, and just took the previous commenter's word that it was outdated, since no one seemed to be claiming otherwise.
But the author also says he runs 10.9 in another partition, and claims to want to run 10.2, although looking closer that appears to be a typo.
