The common wisdom is that Apple computers are more secure than PCs. It turns out this isn't true.

You are misquoting the article. It actually says: "Particularly when it comes to firmware, people have assumed that Apple systems are locked down in ways that PCs aren’t. — It turns out this isn’t true."

Saying something is "more secure" is a little vague, but Apple computers certainly have fewer viruses/worms and have less chance of users inadvertently downloading malware or other maliciously modified software, thanks to the App Store and reputable third party software companies like Omni Group.

Now, if you go about torrenting pirated software, you will likely be screwed no matter which OS you're running.

I've always considered Macs less secure than PCs. I've never known a Mac user to use any form of Antivirus since it's a common belief that Macs are "more secure" than PCs. But the only reason PC has more viruses is because it's the largest used platform and thus the most likely place of success for hackers. However, with Mac's popularity on the rise, I'm sure there are viruses out there for it, especially if you're trying to torrent or download software specifically for Mac.