both Microsoft and Apple share a good deal of technology. Both Windows and MacOS use hundreds of patents shared between the two. Also remember that Microsoft makes a lot of software for the Mac including Microsoft Office which was created by a separate department for the Mac.
Typography - Mac's support of typography is a result of years and years involvement with the pre-press industry. Type-styles rendered with a Mac just plain transfer better when submitted to a service bureau. You get what you saw. If you're into pre-press Mac is the clear winner here.
Video Subsystem - Windows open architecture and PCI bus allow a wide non-saturated video subsystem. Video cards are made which exceed 6 Gigaflops of geometric rendering. Mac, though PCI, has a severely bottle-necked video subsystem so if you're into advanced 3-D rendering, Windows is the clear winner here.
Postscript Support - Mac natively supports both postscipt and PDF formats making them the clear winning here. Again, if you're into pre-press, Mac makes a lot of sense.
Back to Resources Raw Speed - Windows PCs have a serious edge here. Where time is money, processor speed can be very important. Regardless of how hard Mac advertising attempts to claim that the slower clock speed Macs are really just as fast as a PC, it just ain't so and proven so by every bench test out there. If you have the "need for speed" in gaming, software development, 3D rendering and other applications, Windows is the clear winner here.
Color Matching - Apple is the only OS and hardware which supports Colorsync™, the industry standard for "what you see is what you get" color matching. If you want your advertising copy of an egg to come out of the press with the same yellow you saw on the screen, Mac is for you.
Web Design - Now this will be a hot one. In my opinion the clear choice here is Windows. I say this for two reasons.
First, 95% of the people surfing the Web use Windows on PCs. If you want to be able to design in an atmosphere where you see pretty much what that 95% sees, then Windows just plain makes sense.
Secondly, though many technologies are available for the Mac, Windows technology isn't and much of the Web uses this technology. If you want to take advantage of .NET technology or ASP, it's just way easier to implement from a Windows platform.
Ease of Use - I give Mac the edge here, though the difference is pretty small with the release of Windows XP. Windows binary Plug-in-Play is no longer "Plug-n-Pray" and though technologically superior to Mac doesn't get the job done as nicely. By using nearly draconian messures and monopolistic threats, Apple has been able to maintain tight control over makers of third party hardware. What this means to you is an easier to use system, but with much less choice in add-ons.
Back to Resources
Software Availability - Though many might argue that anything you might need is available for Mac, and though almost all generic task software is, industry specific software is not. For example, if you own.. say a lawnmower repair shop, you might want software written exclusively to run lawn mower repair shops. You just won't find it on the shelf or by mail order for the Mac, while you have several to choose from for Windows, maybe even for free or cheap as shareware downloads.
You might argue that you can adapt database and spreadsheet software to need, but it's just not as easy. Advantage to Windows.
Coolness Factor - What can I say? Mac wins. Look at that new i-Mac or the i-Pod. It beats a biege box.