I think Michael Horowitz is being a bit harsh (and I'm guessing that's his entire schtick in a nutshell), but Mozilla's Asa Dotzler summarizes this argument a bit more agreeably, in my opinion. First, the Horowitz bit:
If you surf the web on a Windows computer, you are safer using Firefox as opposed to Internet Explorer.
On June 26th at ZDNet Ryan Naraine wrote about a new bug in Internet Explorer for which Microsoft has no fix/patch. A few days later, he documented how the bad guys were exploiting this bug. That story starts with "Another day, another gaping hole affecting fully patched versions of Microsoft's Internet Explorer browser." We've been down this road before.
But let's be serious. IE is in use on over 70 percent of the world's computers and people aren't actually contracting malware as a result in any massive numbers. (Put another way, if they are, they're idiots.) I understand that the iCabal crowd can't let a Microsoft dig go by, as they're genetically predisposed. But come on.
So here's Asa's more mature take. And he's from Mozilla.
It's pretty basic reasoning. If you take it as given that all complex software has bugs (and browsers are some of the most complex consumer software available,) and all complex, network-connected software has security flaws, then there are basically only two measures that really matter when you're trying to stay safe using a web browser. The first is how hard does the software vendor work to find and fix those flaws. The second is how quickly and effectively can the software vendor get an update in place on your machine.
With Firefox, you can actually see how much work is done finding and fixing flaws. You really can't say that about any of the other vendors -- Microsoft, Apple, and Opera only disclose the flaws found by third-party security researchers so you really have no idea whether or not they're even trying to find flaws in their own software. I sure hope they are, but it's their policy not to say anything about this in public so there's really no way to know for sure.
With Firefox, you get updates as soon as they're developed and tested
OK, it gets a bit self-serving, but whatever.
Here's my off-the-top-of-my-head thoughts about this issue.
Internet Explorer 7. There is absolutely nothing wrong with IE 7. In fact, on Windows Vista, it's arguably the safest Web browser there is. I don't "love" IE 7, and in fact choose not to use it. (See below.) But I'm OK with real people using it because it will keep them safe. And it finally has enough features that's it's not lacking in any meaningful way.
Firefox 3. Mozilla's browser is my favorite, by far, for two reasons. One, it has an incredible extensibility model that has created a cottage market of useful add-ons. You can be really silly with these things and overload the browser, yes. But if you're looking for some key bit of functionality that's not built into Firefox, there's an add-on out there for you. And you can change the UI dramatically with skins, many of which are high quality. The second reason is security. While I do feel that IE 7 is as secure or more secure than Firefox, Firefox does benefit from a pair of things: Hackers love it (and Mozilla) and are thus less likely to target it, and becuase it's used less often than IE, it's less likely to be a target. (This last bit benefits Mac OS X as well.)
Safari. At this point in time, you'd be crazy to use Safari on Windows. Apple is a black hole and I don't trust this software or the way they foist it on people. The only thing seems dishonest to me.
Opera? I know there are fervent Opera supporters out there because they email me every single time I write anything about Web browsers. "When you are going to review Opera [insert version number here]?" "It does [this] and [this] and is better than [Firefox | Safari | IE] at [this] and [this]." Ah, right. I have the same reaction to Opera I've always had. I don't get it. I don't get why people install this thing and I don't get why they like it. I know, I know. That's just the way it is, sorry.
So we can get all partisan and stuff, but the reality is you're OK with either IE or Firefox (and maybe Opera, I really don't know). Just choose the one you like more and browse the Web in a mature, eyes-open fashion and you'll be fine.