This thread is quite old and alot of things have been said, but being neither particularly pro Apple nor pro PC i wanted to raise a few points:
1. OSX isnt better, its different. It might be better for you and your usecase which is fine, but Windows might be better for other people.
2. Dell XPS run Linux pretty fine and Dell actually does alot of work with Ubuntu and pushes driver updates upstream for everyone to benefit. A PC still offers alot more freedom and choice.
3. OSX is not for free. The mac business adds so little to Apples bottom line that they decided to make it free because it doesn't make a difference. Looks noble from the outside, but its cold math on the inside.
4. MS and Apple have totally different business models, Apple makes money with Hardware while MS makes money with Software, so don't compare prices, just don't.
5. You can upgrade a PC from MS DOS all the way to Windows 8.1. The business heritage of Windows is the reason for an enormous backwards compatibility. With Apple anything before Lion (without the Appstore) is hardly usable today. This has its pros and cons of course.
6. MS contributes to Open Source and has public research facilities, Apple couldn't care less.
7. Apple doesn't care for standards and has alot of Software that is not compatible with anything not-Apple. Total vendor lock-in.
8. My encounters with Dells support (business) has been wonderful. Technican at my house the next day, fixing the Problem. With Apple in Europe where there are very few Apple Stores its not that easy.
9. Macs aren't flawless. I had a 2011 15 MBP which got extremely hot and loud under light load to the point where it was barely usable, after a year the screen died. My Late 2011 MBA has a broken speaker, barely working webcam and a depleted battery. Because of only 1 year warranty Apple does not care to fix it.
10. Macs are not cheap. Yes, they tend to have a good resale value, but if you use your Mac for a couple of years and give it to someone else for free or use it until its dead you still spend more money.
And yet, i still use a Mac. Personally i couldn't care less for OSX. I don't use any major OSX specific software, so why do i use it ? Unix, Touchpad, Battery Life and Build Quality are my main reasons. Id like to use Linux, but i am quite certain Desktop Linux will never reach up to OSX, and when it does someone will just fork it and start from scratch.