Dizzyboy,
The answer in my opinion is a bit more complex. You're asking a big question, Mac OS vs Windows. Mac vs PC.
To me the answer is very clear, since I've been an avid Mac user since 1992. Over the years the the Macintosh Operating System has not only kept an edge over Windows (back in the Win 3, Win 3.1, Win 95 days) and then eventually Windows started making significant progress with their Operating Systems.
More recently though, with cross compatibility between documents of all of the industry standard software there's no reason to say "Macs are for designers" anymore. And if you're really in need of a windows application with the Intel based Macs you can run Windows natively (meaning not an emulation) and have the full power of your processors running windows.
So in conclusion, I would say, go for the Mac! Not only will you be pleased as a switcher (since I assume you have had PCs before- or else you wouldn't be asking this question!) because of its design, ease of use and true pleasing performance, but you will also have the best of both worlds, and be able to use Windows should you need to.
In no time you will be a huge Mac fan, and will not believe you had this doubt!
Enjoy!!