The one where the vast majority of web developers live.
The Microsoft world might also be used by large corporations, who also happen to have lots of money, with which you can buy things like software.
(There's also these other platforms based on *nix, but meh :-p)
|pushes button to delete nix|
Hey, where did 60% of my favorite website go? Oh, I'll just google how to undelete *nix... wait... crap!
You're actually discounting the entire world outside of SV right now?
That is an amazing thing to write on the internet.