Macs are better machines...without a doubt, regardless of what you do, business or art.
I've used both, started using Macs in highschool from late 80s to early 90s, then got a PC because they were cheaper and used PCs all the way through until now at the same time I used Macs at work. Finally got a new Mac, a dual processor 2.5 Ghz G5 and it is breathtaking. I've had this machine for almost a year and I don't think it's ever crashed, I can't remember if it has or the last time. As far as graphic design, mac is the norm for Post Script printing and font reasons. For music, the mac OS is more superior so it doesn't crash powerbooks while doing music. I took recording art classes and a couple of midi classes and they all were on Macs for reason being they don't crash(atleast as much as PCs).
Most of the problem lies in usability. Macs are basically plug & play, you don't have to "download" this and that driver, but you still have to on PCs for drivers that maybe old. Also, we're talking about Microsoft, a company which purposely wrote their code for windows to purposely make java unusable, thus discouraging people from using java(they got sued for it too).
When you have an OS like windows that tries to CASH IN ON EVERY COMPANY, they are constantly making updates and changes to their coding just to suit more and more companies. This only dilutes the integrity of the OS and for those companies who wrote their code specifically for Windows but not for the OS changes, those companies are having to make updates constantly BECAUSE WINDOWS WANTS TO CASH IN ON EVERY COMPANY BY CHANGING THEIR CODING TO FIT MORE AND MORE COMPANIES.
If you are just using a computer for simple internet stuff, downloading music, and email, maybe business applications like word, excel, access and stuff, then get a PC...they're cheap. No use in paying a thousand for a mac when you can get a PC for like $300 if you're just using it to play video games, email, downloading music, etc.
If you're doing more sophisticated stuff that requires a more stable machine, you might as well save yourself grief and get a Mac even if it's way more expensive. Your computer will be more stable, easier to use, and you won't have to worry about crashing.
It all depends on how much money you have and what you're going to use the computer for.
In summary:
If I like to play video games(gaming), email, cruise the internet, and download music, I'd get a PC. Your computer will crash, but you're not going to be on it very much anyways, so $300 will do just fine. The ONLY design I would consider doing on a PC is probably web/flash animation and Cinema 4D/Maya, stuff like that.
If you do any kind of design/music and need a machine that won't crash and lose your work and need a more stable and powerful machine, get a Mac. It'll save you grief. As a designer, every minute counts and there's nothing more annoying and frustrating than working and then having a "blue screen" pop up and losing your work.
It all depends on what you're using the computer for and how much money. If money is no problem, go with a Mac.
There's a reason why Macs have a much better resale value. I bought my dual processor about a year ago at $2200(w/tax) and the price has yet to really decline.
If you were to pay $2000 for a PC, a year later, that same computer will be worth only half what you paid and in 3 years, that computer won't be worth but a quarter what you paid and you'd probably buy a new computer after having it for 4+ years.
I've worked on Macs that were 5+ years old and they still worked great.
http://www.apple.com/retail/fifthavenue/