I'm hesitant to write this piece, because there are a lot of people out there who don't analyse functionality - they just adhere to brand preference. It's a bit like the Holden v Ford wars of the 80's.
Anyway, I own a new Mac Mini with 8 GB of RAM and Mountain Lion (as of today), an older Mac Mini with Leopard, and a bunch of Windows 7 machines. I even have a Windows 8 preview, which I can't stand and never use.
I think Mac OS X is not as convenient to use as Windows 7. I think Ubuntu 12.04 is not as convenient to use as Windows 7. I would never by choice use either as a day to day machine. I think OS X is a terrible operating system - as bad as Ubuntu.
There, I've said it. But why? Now, bear in mind that I suspect many of my complaints can be fixed with tweaking, but I don't tweak Windows 7 either.
For document management, the Finder is truly awful. Each of the views in the Finder doesn't display all of the information you need, nor the display you last requested.
Even something as simple as "Don't reopen my windows on next boot" is simply ignored by the Finder. EVERYTHING friggin' opens all the time without me requesting it.
Reopening documents I've finished with is even worse.
Cut and paste files? It seems to work in some scenarios but not others.
Connect to an SMB/CIFS share? Not only is it stupidly slow to connect, it takes 20 seconds to enumerate a file listing that takes 1 second on my slowest Atom powered netbook. Is Apple trying to be funny?
The moment you don't want Apple's defaults - say, moving your music folder, you need to learn about UNIX symbolic links. On Windows you right-click and re-home the folder.
The stupid Finder file views don't make any sense at all.
Desktop web shortcuts always default to Safari - why can't I make them open in Chrome?
Sherlock on the Mac has always been superior to any other OS - that's one good thing.
The Dock is a very odd and not very intuitive GUI element. And by the way, the incredibly subtle little dot underneath running apps is an exercise in modesty. I don't know how to improve the Dock, but it just doesn't feel right.
My Mac is every bit as unstable as every Windows 7 machine I've used. It freezes just as often - say, every fortnight or so.
I'll add to this post over time, but really, five months with the Mac and OS X has made me realise that Windows 7 is the best currently available.