There are many reasons why PC's are actually superior to advanced users than Mac. Lets start from the inside and work our way in.
1. The aluminum unibody may look nice, but its unibody. What happens when I want to open up my Mac to replace the expensive Mac internals? A long, hard, tiring process. I prefer to just have one screwdriver to do all of this.
2. Apple Mac's have poor build quality. 40% of Mac screens go bad, IE screen blots, yellow tinting, backlight no longer works, a ton of things.
3. Ports. Apple has way too many propriety ports and over-priced adpators. I do not want to pay $15 for a 2 inch long VGA adaptor.
4. Pricing. Pricing is a huge issue. I like my money and do not want to pay 2.5x more than what I can get a PC for.
5. Hardware. Apple does not have very fast CPUs or GPUs. Sure, they have an Intel Quad Core. But what if I want an i7 2600K? I can buy that for simply $300. But Apple makes the cost much much more. (you must add the cost of what the upgrade is and the price of the base processor) And Apple's selection of GPU's are not even close to what I would like.
6. Trackpad. I hate not having a right mouse click. Sure, you can do other things to make one, but why is that needed? I want to be able to just hit one button thank you very much.
7. Mac OS. I really hate the Mac OS. Why do I have to press Command+Q (no, the Apple button does not stand for Apple+Q. It is called the command key) every time I want to close an application? I want to just push the big red X button. And the dock, oh how much I hate the Mac dock. I do not want to see every single application there. Only the ones that I use the most. The others should be organized into the Start Menu and I can easily search for one if I want to, no need to open up an entire window to do so.
8. Mac's lack of software is greatly depressing. There is a ton of software on PC that is not useless and only for more advanced users who know what they want. As for iTunes, iTunes can simply go die in a hole. I would be much happier with being able to use something else for my music and syncing. iTunes is extremely slow and I do not want to back up my ENTIRE iPod Touch before being able to sync one song.
9. Mac's may outlast PC, but why pay $2000, or $3000 for something that will be outdated in a few years. I can spend $1000 for a PC and easily upgrade certain parts for simply $200. With a Mac, I would have to purchase an entirely new Mac. And PC is NOT a "little" cheaper. It is A LOT cheaper.
10. Aluminum unibodies may be nice looking, but who the hell really cares? Oh look guys, I have $2000-$3000 to spend! I would much prefer something like a nice flush, matte black laptop with a few cold cathode lights in the right place.
11. As of right now, the top 500 fastest running computers (not super-computers) are PC's. Why is that? Simply because you can put a Intel Xeon W3690 @ 3.47GHz CPU or a Intel Core i7 995X @ 3.60GHz and at least with Windows, there aren't millions of useless things running in the background that can't be stopped which bogs down the OS.
The verdict: if you know what you want, and know what you're doing, PC will be the obvious answer to you. If you have no idea what you're buying and want something shiny and would like to spend a few months salary on then go ahead, buy that fancy metal box.