Lets put everything in it's own prospective here. Mac's are no different from any other Intel computer, they all have the same Intel processors, GPU (Graphic Processor Unit) be it a ATI or Nvidia and motherboards
When it comes to operating systems Mac OS/x is Mac's own proprietary operating system, which only allows user to do what mac want them to do. That is to be under the full control of Apple Mac, Users do as they say, not do what the users want to do, Mac controls the widget, the widget controls the widget users, that is why most universities don't use mac's they don't have control of Mac hardware,
Plus Mac OS/x (BSD) is not a standard operating system
You have touched on a subject that the other answers never give an answer on which was "Linux" They never mentioned anything about Linux the reason for that is they don't know anything about the operating system, I will explain why universities are now using Linux,
(1) it is free Open Source software
(2) they can do what ever they want with the operating system
(3) it saves Student money they don't have to buy expensive window OS and application software
(4) most of all it save the universities $1.000's a year in MS license fess for every workstation they have
(5) Linux is faster, more secure and stable, it is always up to date with the latest and greatest technology,
(6) Linux is supported and developed by the biggest IT companies in the world
I could give more reasons but I will leave it there