This one's close. Apple's Spotlight--the search feature built into Macs--is handy indeed. But when you get down to brass tacks, Windows 8's Search charm is better.
Again, Windows 8's Search isn't perfect. Unlike in previous versions of Windows, it isn't unified; the Search charm dredges up installed programs alone on the first pass, and you have to click separate listings to see the Settings and Files results. But, crucially, the Search charm also allows you to sift through specific apps to locate more-narrow results, seamlessly and quickly. It's a wonderful feature. Plus, if your systemwide (or app-narrow) search comes up fruitless, you can select the Bing app within the Search charm to scour the Web for your precious item, lickety-split.