1. Usability, as Apple likes to call it. Windows is hardware-based, with vendors competing for better specs. With Macs, it's all functionality. If hardware isn't a problem, then why overindulge in something you don't need?
2. Design. Sexy MBP.
3. Battery. Kickass MBP.
4. Program Variety. The main arguement people have against Macs is that there aren't as many programs for Mac than for Windows. They leave out one thing: Macs can run Windows AND Linux. Which means PCs, which can't run Mac OS X without hackintoshing, have less variety in programs than Macs.
5. User interface. I like simplistic, utilitarian glassy design. Snappy, too.
6. Speed. Quad-core 15" can't be beat. Unless, as said by T-pain,
IT AIN'T HARDCORE UNLESS IT'S HEXACORE! MEGAGIGABYTE SON!
7. Compatibility. iDevices are integrated seamlessly with Macs, as opposed to PCs which have less integration.
8. Upgrade. I was due for a computer upgrade anyway.
9. Future-proofing. I see people still using PowerBooks, and that kind of longevity is nonexistent in PCs.
10. Specs. Kickass CPU, good screen resolution, decent graphics, etc. I tried configuring similar laptops as closely as possible, but they either ended coming short of my expectations or looking ugly.