As a matter of fact a Mac is the worst of the three options I could imagine to give to my mum. I keep saying to Mac fans, first try to explain it to your mum. Have you tried it?
It's all the small unintuitive things, like "x" doesn't close the application. There are no hints for accomplishing basic tasks like renaming a file or moving a file (Finder doesn't do cut, only copy). And so on... I consider myself experienced with computers, but on OS X I have to google how to accomplish the most basic tasks.
Really, please try it. You know, explain it to the kind of person who has to write down every step on paper. (Not that my mum is that bad - actually I have her on Ubuntu and she is doing fine). So that person has to write down "don't close the application with x, use cmd+q" - it's ridiculous.
Gestures look great in presentations - but how do you learn them? There are no hints in OS X as to what to use (OK, I can remember pinching and scrolling - but I don't resize pictures much, so guess what, it is not THAT helpful after all).
It's fine if people love their OS X (for whatever reason), but the claim that OS X is simpler is definitely not true.