As a graphic designer, and as someone who's used both Macs and PCs, I prefer the PC. Using a Mac for graphics work used to be a necessary evil. Now you can do anything on a PC you could do on a Mac, and it will probably end up costing you a lot less. And if you're like me, and enjoy building and upgrading your own systems, the choice is obvious.
My only major gripe is that Microsoft needs a strong competitor, because their products are often the suck but finding a viable alternative is tough.