Your forgetting the user base...
The whole thing about different Operating Systems your forgetting is that they appeal to a different user base.
Windows: Gaming & set software is the advantage & that its had an easier time getting to it's users.
Apple: Gaming & Set software is the advantage. Ok, not as much gaming on the Apple, but Windows is the main OS for gaming, The Dreamcast, Xbox 360 & I'm sure theres other machines that use Windows for gaming. The Apple's are made for photography & video editing.
I prefer to use Apple for day-to-day tasks. Even my girlfriend prefers OS X to windows. Mainly because it works, you've got no fear of virus's & you don't wait ages for it to load.
I'm really keen on Windows 7 when it's released, enjoying the beta. It does remind me on OS X in certain way's. But its good for gaming. But then there's only certain games I have for the PC. I mainly game on the 360.
So for me, I switch to what works best for the task in hand & thats how people should look at things. If somone prefers using Windows, let them & visa versa. I'm no fanboy, but Apple's Hardware & Software just works for me. No problems at all. Everything connects via wireless with no problems, streaming to my xbox, no problems, install & un-install, no problems, no hidden files left, they just go when I ask them. Touch wood, I've been using macs solidly for 2 years now & never experience as much as .01% of problems I had in XP & Vista. I'm still learning OS X more & more each day & love it more & more.
Dual booting OS X & Windows 7 will be a premanent thing for my machine when Windows 7 goes on sale. & remember, without competion, at least none of the OS's get boring or stale.