Let's see if I can sum this up:
All-around speed: Each platform's high end systems are probably about the same for your average user.
Graphics applications: I guess this would go to Macs, though I wonder if its mostly for historical reasons. Sure, for hugely processor heavy jobs, I've heard Mac is better. But, for example, my friend's dad has a small advertising firm and the whole office uses Mac's for graphical publishing and such. But if all you're doing is using Photoshop and various Adobe apps, can't it be done just as well and quickly on a PC? I suspect that all the apps were originally for Macs and people just got used to them and there was no good reason to switch.
Gaming: PC, hands down. The number of games dwarfs that of the Mac. And I can't think of any major titles that are released on the Mac that aren't on the PC.
Utility programs: Equal. Both can do the web, email and word processing equally well. And this is the vast, vast majority of computer use, isn't it?
Fixability: Others have stated that Mac's are easier to fix. But I'm going to counter this by pointing out that there are way less people knowledgable about Macs to give assist. My ex-gf was foolishly advised by the school computer store(computer's were mandatory) to get a Mac because it would be easier to use and fix. But NO ONE knew even the most basic functions and troubleshooting so she was stuck with a half broken-down Mac. So if you're going to go Mac, make sure that you know a person or two from whom to get help.
Usability: I can't really say. I've been using PC's for so long and so used to them, my ability to judge whether XP is good in this regard is clouded. I don't know if I can use it well because it is designed well or if I'm just accustomed to it. And my ability to judge the Mac is scewed because any design other than one like XP will be difficult for me. Or perhaps Apple needs to consider that the majority of new users have a PC background and design the interface accordingly? I can't really say though since my Mac usage is limited.
Stability: Well, we've got anecdotal evidence against either side. But I've heard that Mac's are quite stable and my experience with XP has been that it is quite stable. So its probably about equal.
Price: PC's seem to be cheaper, but Mac's really aren't that bad. We're only looking at a couple hundred dollars difference at the high end.
Style: About equal now. When Apple came back on the scene 4 or 5 years ago with the colorful ibook and iMac, the Mac's were way ahead. PC's only used to come in plain beige boxes. Now you can get them in a variety of styles and can custimize with flourescent lights and such.
Image: Macs have kind of a hip image that might appeal to some people. Not teenager hip, but more like a upper-middle class, Saabish, pacific northwest type hip.
History: Due to Apple not allowing third party companies, the Mac didn't skyrocket to popularity like the PC. We've all pretty much grown up using PCs and this is with what we are comfortable. Users' history of using PC is a hugely powerful force and is not to be underestimated. Now Applie is really pushing to gain marketshare and I think this history is the biggest obstacle to overcome.
And the short answer is: if you play a lot of games, go PC. If you don't, then either is an acceptable choice and up to personal preference.