When it comes to security, Ubuntu and Mac are pretty much dead even. Both Linux and OS X are Unix-based operating systems, and have nearly identical security models. Users of both system can feel safe from viruses and other malware.by https://wiki.ubuntu.com/mb_webguy
In terms of price, Ubuntu wins hands down. Apple software tends to be rather expensive, while Linux and the overwhelming majority of software it uses is absolutely free of charge.
In terms of usability, it's a toss-up. One area in which Apple is quite successful is the user interface. That's why so many mp3 players tend to copy the iPod to some extent. OS X is no exception, and has a very nice interface. On the other hand, arguments could be made for the usability of Gnome, KDE, and Xfce as well, especially considering the amazing degree to which these desktop environments can be customized.
Which brings us to customization. Ubuntu has the edge here. The options for customization of Linux are staggering, with multiple desktop environments and window managers from which to choose, which themselves are highly customizable. OS X can be themed and customized, but not even close to the degree of Linux.
When it comes to software, it's a mixed bag. Mac is more commercially supported than Linux. For most tasks, this doesn't matter as an abundance of FOSS alternatives exist for most commercial applications. And for most purposes, this gives Ubuntu the edge, since the software is just as free as the operating system. If specific applications are a priority, however -- most notably iTunes -- then Mac has the advantage. There's no clear winner here, as it really depends on what software you feel you need.
Of course the mention of iTunes brings us to the issue of freedom. Apple is even more notorious than Microsoft when it comes to vendor lock. Everything Apple produces is proprietary and made to work best (or only) with other Apple products. iPods, for example, are practically useless without iTunes, because the iPod uses a proprietary transfer protocol. Since Apple won't release the details of this protocol, no other software developers can develop iPod management software without essentially reverse-engineering the protocol -- which Apple periodically alters. On one hand, this gives OS X an edge against Linux for people who use other Apple products. On the other, it's extremely annoying and limiting. If you don't like companies manipulating you and dictating how you use their product, then Linux clearly has the edge. While I'm tempted to say this is another tie, I can't in good conscience say that vendor lock is in any way an advantage, except to the vendor. Free and open-source wins.
Because Linux is open-source, anyone can do anything to it, and can see exactly what's going on under the hood. This is part of the reason Linux is a safe computing environment (and arguably slightly more secure than OS X) -- viruses are hard to sneak onto a system when people can see the source code. No restrictions or license agreements restrict your use of your own system. However, because it's not a commercial product backed by a corporate entity, the means of technical support is radically different. For some people, the lack of obligatory customer support is a failing of Linux. Others like not having to rely on a single entity to provide technical support, and prefer the support provided by the Linux community. As a matter of personal preference, tech support is another toss-up.
So... which operating system is better? Well, "better" is a relative term, in more ways than one. In my own case, I'm perfectly happy without iTunes or any other Apple products, so there's no compelling reason for me to use OS X in order to use those other products. I also prefer a free product over an expensive one of equivalent quality, and prefer freedom over the lack thereof. So for me, personally, I say without any hesitation or reservation that Ubuntu is the better operating system. But this may not be true for someone else who loves using iTunes to shop the iTunes store for videos to transfer to his iPhone. For that person, who apparently has a much greater disposable income than myself, Mac OS X is the better choice.
It just depends on your priorities.
PS: This is two years old and usability of Desktop Environments have improved a lot now!
PPS: I was able to post this only because it was licensed under Creative Commons and I recommend any poor soul still reading my blog also to do so; It's good for the world. :-)
