Black, or with milk? Sugar, or no sweetener? People love their morning coffee, and they are very specific about it. And it appears that more java addicts are starting to buy it at Dunkin' Donuts instead of Starbucks lately. Shares of Dunkin' parent company Dunkin' Brands (the company also owns ice cream shop Baskin-Robbins) are up 10% this year and 25% over the past 12 months, largely due to earnings and sales that topped Wall Street's forecasts. The stock is even trading at an all-time high. Talk about a caffeine jolt. Starbucks, on the other hand, is flat this year and has lagged the performance of Dunkin' over the past year. One reason? Starbucks is having some growing pains with its mobile app, which allows customers to place and pay for orders in advance and skip waiting on line at the checkout counter. Starbucks incoming CEO Kevin Johnson, who will succeed founder Howard Schultz next month, said in the company's earnings call in January that the success of the app has had some unintended consequences.