Top 3 reasons Mac users/adverts give for choosing a Mac over a PC:
#1: BSOD
I think apple is a bit behind the times. Firstly, the OS is now in a pretty stable state and it takes a lot to completely crash the entire OS. Also, the BSOD is really the result of 2 problems; user error and the wide variety of programs and hardware configurations. It is inevitable that some conflicts will occur and there is almost always a simple solution within reach. Macs may be less likely to crash because they offer the user less freedom and do not have as many choices available for hardware and software.
#2: Mac's are good for editing
Macs are useful for editing, but claiming that PC's can't perform the exact same tasks using some of the same or similar software isn't true. Often PC's can offer a similar or greater experience with cheaper hardware. PC's also have plenty of support for many different video codecs, playback programs and image-editing tools.
#3: PC's are boring and for "Nerds"
This stigma really doesn't need debunking. MS pretty much covered that in their latest series of adverts. Windows and PC's are used by millions of professionals and home users alike for a wide variety of different purposes.
It really isn't a big issue since both PC's and Mac's are available and their usefulness is constantly expanding. It would be nice if Apple would stop throwing their poo around the cage though. Or they could at least attempt to update the poo they are flinging.