I have been an IT support person, a programmer, and a creative professional (digital design as well as audio production/recording), and used both Macs and PCs for all three, and while I may be biased because I have never actually owned a Mac, I really don't think any of the usual arguments for Macs hold water any longer. The hardware is now (as another few posters mentioned) essentially the same as a typical PC (Intel/x86/64 arch), the software is interchangable (by that I mean you can install OSX or Linux or Windows on either machine).
The idea that Macs "just work" is preposterous to me, because I have never, ever seen a Mac "just work". Nor have I ever seen Linux "just work" (except for a few simple distros like Ubuntu, where it makes all the decisions for you). And of course it would be foolish to argue that Windows "just works."
For me, the choice is still Windows when it comes to professional work (Linux would be a better choice if all the same software apps were available). I have been working on a home recording with a band, where the work is being done on a Mac using ProTools, and every single session there is some kind of stupid technical issue that takes up precious time. At home on my PC, I don't have the same kind of trouble, at least not to the same degree or with the same consistency.
What it comes down to is what User Interface you're more comfortable with. Both are equally capable of performing the same tasks. But one is about 1/3 the price and does not require that you go to one specific store to get replacement parts.