For one thing, Apple's UI is simple and non-intrusive. These days, I rarely minimize windows, preferring, both on Mac and Gnome, to move them out of the way to a new workspace. File management is also something that's not as important anymore - apps don't work that much with files and the distinction of what's local and what's not is blurry with iCloud.
I find Windows a bit confusing. There's a start menu, but there are also icons on the bottom of the screen that show some, but not all, applications available. Configuring stuff is a nightmare - vendor applets and system applets compete for functionality.
Both Windows and the Mac make a stupid blunder in splitting app and system updates. I don't want to search (or be prompted) for updates from two different places. I don't care whether my text editor is or is not part of the system - it's part of MY system. On the Mac, it is a regression - a couple releases back, there was a unified mechanism for updating software. Now, iWork is on the App Store and, for some reason, Safari updates with the OS.