Mac OS X is an incredible operating system: powerful, stable, and
beautiful. But there are times when Linux offers a better solution. Two
that come to mind immediately are for dedicated servers and high
security applications.
Some qualifications and context are required to understand my
reasoning.
Dedicated Servers
Being based on BSD, OS X is a fast, stable, operating system. It
also ships in a reasonably secure state. So why would I suggest that
Linux makes a better server?
The answer is flexibility.
Apple offers dedicated OS X servers in a rack mount form factor,
branded Xserve along with Xserve RAID
storage. However, you get a sense of Apple's consumer focus by noticing
that Xserve products don't even appear on the main Apple Store page. You
need a dig a little to find them.
As a small office or workgroup solution, especially in a Mac-savvy
shop, Xserves are great, but when you get into a mid-sized or large
organization, the flexibility of Linux becomes more important than
saving a little setup time.
Since OS X ships with GNU C compiler, Linux only has a slight edge
in available software, but it is definitely easier to do things like
customize the kernel. Replacing major components like the MTA is also a
little easier in Linux, because the integration with other applications
usually isn't as tight.
Yes, hardware flexibility is the biggest advantage of Linux. You can
load Linux on an Xserve, an old PowerPC box, IBM blade servers, or a
super cluster of generic servers. And it's easier to upgrade a PC-based
Linux box as your needs change.
In most cases, Linux can be deployed less expensively than Xserve,
making it a better value.
High Security
While the focus of the article is OS X and Linux, the security
context requires that I mention Microsoft Windows. I have fairly in
depth knowledge of all three systems and run all systems to some
degree.
There are a lot of metrics that can be used to measure security, but
it's as much art as science. If you start with the operating system,
you can look at past history, the number of known exploits, the
severity of known exploits, and the malware ecosystem. You have to
account for the out of the box configuration, included software and
services, encryption options, and the ability to apply patches. Then
there's the hardware - physical security and locking options, processor
and architecture exploits, portability. It can be mind numbing.
Turning the myriad of security metrics into something quantitative
is extremely difficult. My qualitative sense is that on a scale of 1 to
10, with 10 being the highest level of security, Microsoft Windows
rates a 2, Mac OS X rates a 7, and Linux rates a 9.
Ultimately, the biggest factor in the ability to secure a system is
the ability to trust it. On trust alone, Linux is head and shoulders
above the rest. Let me explain and offer a few examples:
Microsoft Windows: 2
The Windows
stealth patch incident is a glaring example of an untrustworthy
system. This is a case where Microsoft forced a system update on
users regardless of their preferences or whether or not they wanted
the update. There was no notification and no warning; they simply
replaced some system DLLs. Actions like this beg the question, "Who
really controls a system running Windows, the owner of the computer
hardware or Microsoft Corporation?"
Another example is the architecture of the Windows
Product Activation (WPA) feature. It requires that Microsoft be
able to remotely reach out and disable any computer it thinks
is running unlicensed software. The fact that WPA sometimes flags
valid software as unlicensed is a growing concern for some. It is a
"guilty until proven innocent" scheme.
The only way I use Windows now is disconnected
from all networks.
Combine the built-in features of Windows with the giant universe of
active malware that comes with the platform, and you have a system that
screams insecurity. Even with the latest patches applied, the latest
anti-virus and anti-kludgeware, and locked in Fort Knox, I would not
trust sensitive data to Windows. The only way I use Windows now is
disconnected from all networks.
Mac OS X: 7
Being based on BSD, a Unix-like system, OS X starts out far ahead of
Windows. The security model is proven (to this day, there have been no
OS X viruses or malware in the wild), and the default
configuration is generally safe with no unnecessary services running.
Mac patches require approval before they are applied, and there is
nothing as virulent as WPA waiting to shut you down if you plug in one
too many peripherals.
I love using Macs (I'm banging this article out on a Mac), but there
are two things that limit my ultimate trust. One is the lack of open
source for the some parts of the system, and the second is the track
record of Apple toward users. Without complete source, I can't be
reasonably sure that Apple won't force a Windows-style stealth patch
someday. In fact, I am reasonaly sure they have the ability to do
so.
The hyperactive Apple legal department also gives me pause. Could
the government or Apple's own legal team have forced the addition of a
backdoor in OS X or the ability decrypt FileVault data without a
password? I doubt it, but with no way to find out, my trust is limited.
Clearly, I trust OS X far more than Windows - and I trust it
enough for everyday use.
Linux: 9
Linux addresses all the major trust issues I have with proprietary
vendors. I can be certain that no patches will be applied unless I
permit it. I can control precisely the software I want to run and can
remove any software I don't want to run. I have complete access to all
source code, along with many other people, so security issues can be
found and fixed quickly.
There is no phoning home and no unlicensed software by definition. I
can use encryption algorithms that have stood the test of time and
proven strong. I have a strong level of confidence in every part of the
system - I trust it, even connected to the big, bad
Internet.
The only reason Linux doesn't get a 10 is that the source base is so
big that something could be lurking there that doesn't get detected
right away. Still, for a high security applicaion, I would choose Linux
every time. 
Keith Winston is a recent Mac convert after five years of Linux on the desktop. He also writes for Linux.com and created CommandLineMac to focus on the Unix-y power of the Mac. If you find Keith's articles helpful, please consider making a donation to his tip jar.
