A general overview.

The fight between PC's and Mac's have been around since.. well the first ever stupid fucking fanboys, to be honest. Let's kick this post of with a nice general look at things shall we?
The PC, an acronym for Personal Computer, and has come to mean specifically, a Windows based OS[Operating system for those not in the know]. Windows, is of course, the baby of Microsoft.
There are currently 6 Windows OS generations, the generations are dated by the kernel. You probably don't know what that is, and have no need to know what it is either, for the moment at least. The 6th and latest Windows OS, is Windows Vista, which is then split down into.. well quite alot of different packs. The 5th was Windows XP, the 4th was 95/98/98 SE/ME, the 3rd was quite simply Windows 3(.x), Windows 2 and 1 were also just numerals, no fancy naming systems needed for them.
The Mac, the shortend version of Macintosh, has also been around for several generations, it's the brain child of Apple Inc. There are several products flying under the Mac banner, being the Power Mac G3, G4, G5, the iMac, the eMac, the Mac mini, the iBook, and technically the Xserve, the latter being a Server system, which while running on Mac software, most users will never see.
There is also Linux, but considering that has next to no fanboys, I think we can leave that.

Those are the two main user demographics, who each seem to think the other system is crap.

The PC, in general, is viewed as the gaming OS, and also the home-users OS.
The Mac, in general, is viewed as the professional's OS, the OS of someone who only uses computers to create something(ie computer graphics).

These stereotypes, are quite true, while also being incredibly hollow. There is alot of overlap between the systems, and as I hope to reveal to you, it really only comes down to which system you happen to like the UI more on, unless of course, your doing video, or professional Music editing. In those fields, I doubt you need to me to suggest which system :x

For things like Graphics editing, everyone quite rightly looks firstly at a Mac, however the PC is a seriously under-rated system in this. Practically all software that will run on Mac, has been simultaneously designed for the PC too. That's right ladies and Gentlemen, Adobe's Photoshop can actually run on the PC! Shock, horror!
The functionality remains the same across both systems, both will do exactly the same thing, however, the Mac version, *is* easier to use, especially once you start having twenty or so windows open, the ability to view all the windows, and quickly select one is one hell of a feature, and unfortunatly for PC's, is built right into the OS. Alt+tab, simply isn't going to cut it. However, those differences apart, the are exactly the same versions, and will perform the same.

That is but one example, and I think, I'll give it a rest for today.