well pretty much...
some like mac, some like windows, i use both because i have to. But, linux is the all time fav. Even with OSX and scripting possibilities etc mac doesn't quite cut it. hardware support is not what i need, ie too hard to upgrade, too expensive.
i guess mac is preferable to windows, securitywise and their approach to incorporate x11 support etc, but i've grown up with windows and that is probably why i use it, in addition hardware is cheaper.

I mean, mini-mac is a great idea, but a mini-itx and linux will come out cheaper.
so, basically, i chose OS based on that I'm a cheap bastard.

[edit]
did some thinking in the shower (best place for it, in my opinion).
It all comes down to what you want.
If you are a subscriber to the latest video and soundcards, my bet would be windows.
Same thing if you're a fsp junkie (which i'm not).
if you're looking for a secure system, go linux (or perhaps mac).
cheap -- go linux
easy to set up -- windows, and maybe mac.
highly customizable -- linux.
scripting -- linux, or perhaps mac (i actually tried VBscript the other day, which is fine but a bit complex, even for easy stuff).
good hardware support -- windows
there is probably more stuff to consider, but the point is that it's a trade-off between what you want, what you get, and how much you have to pay for it.

For me linux is the solution to most problems, it has free statistics packages, better than most commercial stuff i've tried (R-project). It got pretty good graphics programs (gimp, inkscape) and it has annoyingly good programmability (it's built for it). At work i deal with large sound file-databases and statistics around that (spectral content, etc). here linux programmability and scripting comes in really handy, plus i get support for high end sound cards. Therefore, I'm a strong proponent of linux.

i think that wraps my shower thoughts up. [/edit]

cheers
-.erik