I have to agree with the first guy. It is mostly about preference. I hate Macs, but, thats only because Ive used a mac for most of my life and I know the Ins and Outs of it. The way I like to think of it is this way. With a mac, you are subject to its will and must simply comply with it. With a pc, you are the one in control; it will bend to your will. Now, here is the catch, with a mac, you can just let it take charge and simply follow along. With a pc, you can force your will over it and get what you want. Depending on the type of person you are, your preference will be different. A person who is very demanding and pushy will hate a mac because it just doesn't have any options. Those who like being taken care of and have no wish fight with their computer, will not like a pc.
If you want to talk money, a pc of similiar price to a mac will always perform better and just have better hardware. If you want to talk choices and variety, PC wins this category with numerous venders (which can be discouraging to some people). If you want software, the mac comes with better standard software. iTunes beats musicmatch, iMovie beats MovieMaker, garageBand beats sound recorder, etc. *prepares for flames for such statements*. However, the pc has a lot more software available that is more varied, and much more flexible (remember, macs don't like to give in). Try a simple search on the internet for software, you are going to find lots of .exe files. I tried demonstrating this once and found linux software before I found mac software (which is why I always inlcude the word "mac" when I search for mac software). Also, the pc has a lot more and a lot better professional level software available for it. Sorry mac-people, but final cut pro is in fact NOT the greatest thing since sliced bread.
Then there is the issue of hardware and upgrading. For macs, upgrades basically don't exist. If your mac is not quite good enough, you should just toss it and get a new one. It is this very attitude of Apple that got them sued over their iPods (why replace the dead battery in your iPod when you can just buy a new iPod every 6 months!). Also, pc hardware tends to be better. Take a look at the iBooks. They had some serious overheating problems (though exploding batteries are not exactly better). At least, Apple admits their PowerPC chips weren't cutting it, which is why they jumped to the PC's intel chips (that's right! pc did intel before it was cool). I was quite happy to hear apple was going to be using nvidia video cards (mac-users: video cards? what are those?). I know! crazy isn't it? This kinda leads to the next point. I have to question how much the video cards are for gaming. I think they are really for 3d rendering in some of the media workings that macs are known for. The only thing PCs have more of then software is GAMES! which is perhaps the biggest deficiency of the mac. sure, you can get oregon trail (an awesome game!) and play some zuma but really, there just aren't as many. macs are not gaming consoles.
Now, except perhaps the gaming thing, everything I listed probably doesn't matter for the average user. Which is why the mac is so popular with the typical end-user (despite splitting <10% of the market share with linux). Oh... I didn't get to talk about linux... oh well, maybe next time.