Macs have the advantage that they are selling a complete packaged system. MS makes Windows and it could be installed on a laptop made by Toshiba, Dell, Sony, etc... Or a desktop made by Alienware or some bloke in Basingstoke from parts he salvaged from other computers. Or even a touch screen system that books tickets at an airport, rail station or books patients into a doctors surgery. My point here is that the fact windows works at all is a credit to MS. And the old line "Mac is more stable because its unix based" doesn't wash any more. Years ago yes when Win98 was patched up to the eyeballs but now, no. I have used Windows in a professional capacity since 3.1 and now run 7 at home and XP at work. I've used Macs since the days of the all-in-one Apple Macintosh computer with the handle in the top, and I've used UNIX solaris machines for years as CAD workstations. Let me say that in all honesty and in my experience Windows 7 is as stable as MacOs or UNIX.
Macs are great because they're pre-packaged they work fairly well with common tasks for people they're aimed at: photograpy, video editing, web editing etc... Yes I would say they are better than a standard Win PC at this. But if you're running 3D CAD workstations networked in a large company, with complex file systems, Macs are next to useless. For a start upgrading them is a lot harder and general maintenance likewise.
I can bet that no TOC in the UK uses macs for day to day work or in depots for maintenance schedules, work cards etc... And every F1 car on the grid was designed on Windows or UNIX. NASA use windows... So while Macs are brilliant at many things (but are overpriced in my opinion), they're not "the best". Because I don't think any of them are the best. Horses for courses.