Our nerdy, yet sexy—in that librarian-glasses-wearing sort of way—sister Lifehacker did a side-by-side comparison of the announced features in OS X Leopard and a recent Windows Vista beta. Their conclusion? It's close, but Leopard pulls ahead with stronger built-in apps (for example, iCal wins over Windows Calendar) and by sheer number of included programs.
Hop on over to get a detailed look.
Mac OS X Leopard and Windows Vista side by side [Lifehacker]