I’m posting from a Hackintosh right now, and I use a mac laptop when I’m on the road working. I use Windows machines at school, and Macs at home, as well as when I’m working on my laptop.
1: OSx is customisable, if you have enough technical expertise, you might have to do a little more research than a Windows person, but the opportunity is still there.
2: OSx is much cleaner, and significantly easier to use. I use both operating systems on a daily basis, although I am on my Mac a little more often. I’m far more productive on my Mac, I can accomplish things faster, I can navigate through files faster, and the organisation of files seems so much more intuitive – or rather, everything does.
3: For web development, the apps available are significantly better, and certainly more aesthetically pleasing. It’s a great feeling when I switch over from a Windows box at school to a Mac, everything seems to be more free of clutter, and I have Alfred back. (if you don’t already have it, alfredapp.com, check it out)
4: Hardware is more aesthetically pleasing, and there are a ton of little things that make it seem so much more robust, more solid than school computers, or non-mac-laptops of colleagues.