First of all I would follow most of Jamesbuk's advice, and second I would read good old
Ken Rockwell... Once I had read that I would consider everything he says and realise it pretty much covers all the "plus" points of macs that mac fans wheel out, then I would realise most of it is either **** or older than time and with no relevence to modern Windows machines.
First thing you need to realise is (and I assume you already know this) that Windows and OSX run on exactly the same components, they only have a different case and operating system. Then you need to realise macs do get viruses, crash, need upgrading, can slow down, have problems, to a very similar extent to windows PC's.
Both quality prebuilt windows machines and OSX machines will "just work" out of the box and will work equally well for good, unless you touch something you shouldn't do (which appears to be what a couple of the mac users in this thread seem to be alluding to, such as pointing out it removed their upgrading fanaticism, because it is harder to upgrade partly, or there isn't the upgrade culture with macs, not because macs can somehow make their machines work faster/as fast as new machines. Although along with a couple of other myths that mac users seem to like spreading this could be due to the seemingly mythical technology Apple use in their machines

).
And on the mythical technology side, apparently Macs just start instantly, whereas windows machines take an age... Well wrong, Macs take just as long to load from a cold start, and when in sleep mode both will start in 1-3 seconds. If that wasn't the case then Apple would have found the holy grail, sme hind of hard disk technology that could unload a Gb or two of information in a ssecond or two...
As for software, Macs do come with some useful software, as do Windows machines (much to the displeasure of the EU

). When dealing with the photo side of things, Photoshop is pretty much the main piece of software, followed by lightroom, both of which were written for windows machines, and ported over (with a couple of problems) to Macs, in that respect vista is actually the better OS for photo editing.
I think the main reason so many photographers and creative people use macs is not due to the fact they are "better", just that it has become the culture to use them, especially if you are a "pro".
So the jist of it is strip all of the usual rubbish away and just get to the main differences between th two, the OS. Do you want to try something different (just because it is different, not because it is better) or do you want to use something you are more comfortable with/have experience with?
If you want to try something different, just for a change/ realise it won't "change your life"/ and/or you have the money then go for a mac.
If you just want something that works out of the box, then go for either
If you want something you are comfortable with/ feel cheated by the price/ works with existing software/ has greater backing for software etc./ plays games, then go for a Windows PC (if prebuilt go for something from a good manufacturer)
If you want something unique/ something you can tailor to your specific needs/ want something powerful yet cheaper/ want to fiddle, and you possibly have a reasonable understanding of how to build a PC then build your own (remembering a little bit of research on component compatibility, which is pretty much universal, will mean once you install the OS, it should "just work" too).