Wednesday's update to Google Now adds functionality similar to the new Passbook in iOS, and this is a key point of competition. You may not use them yet, but these scannable passes are going to be everywhere, and you're going to want the phone that handles them the best.
Mobile platforms compete on convenience. Now that Android and iOS are both highly refined, the choice between them comes down to which one fits more seamlessly into your everyday life. Passbook, which came out with iOS 6 this year, was the first feature of iOS that stepped into the realm of check-in and check-out at real-world businesses, a transaction that's becoming more digitized all the time.