My son has a Windows PC, MacBook Pro and a Palm Smartphone. I just asked him and he's wouldn't switch the MacBook for a Windows laptop. Me ? ... I'm too old....I can't handle bouncing back and forth between two OS's....er 3 OS's.
Here's how to get the best of both worlds:
Get the windows PC. Now put linux on it and say hi to Unix and all the advantages of mac, with better compatibility and support. What about bootcamp you ask? All bootcamp is is mac adding the ability to install windows and dual boot on their computers and calling it a feature. Yep a feature of mac is the ability to run windows. Of course, since you bought a computer you get windows for free already and can dual boot.
Alienware is alot of money for a paint job. Lenovo laptops, especially their expensive once, are solid. Macbook Pros are pretty nice, but just not in the price range I like.
What other external devices will you be using with the laptop? If it's alot of Apple hardware then Mac OSX is going to be a good choice, but Windows should work just as well in most cases. If you want to sync Windows Mobile phones or something, you might have issues with OSX. I don't have a Windows Mobile phone or OSX to say for sure though, so I could be wrong.