Thanks to an accident of history (NeXT) combined with Apple killing backwards compatibility with OS9 down, they have a really developer-friendly API compared to Windows. On a purely technical level, Apple is far more developer-friendly than Windows.
They are doing their very best to shit that all away though, when it comes to the legal and backwards-compatibility side of things. That's one reason I doubt I'll ever spend my money on Apple.
1. the Win32 API is not the only thing to develop on Windows with. Personally, I find C# &.NET to be much more comfortable to program in than Objective-C & Cocoa.
2. There is no silver bullet. Some platforms are better at some things than others, but it's largely a matter of accidental complexity.