"PCs are better because most people have PCs"
This is completely true. I use Linux at work and it obviously it is a superior operating system if you need to be able to actually need to be able to write scripts and integrate either the OS tools or your programed tools with file system.
But if you just need to point and click most of the GUI's are pretty much all the same now linux(gnome,kde), mac or windows.
Hence for the average joe windows is better because more people use it. Same goes for alot of computing software ie office, facebook, ebay, driving on the left.
If you need to communicate with people which is generally what most work on computers is ultimately for then compatibility is most important.