Browsers are notoriously inefficient with data because they are designed to render a wide variety of web elements that you don't really need for betting. An installed application, on the other hand, only transmits the actual odds data, which saves a significant amount of bandwidth. You will notice that the app loads much faster and uses a fraction of the data that the mobile site does. It is a much smarter move for your data plan and your battery life if you plan on checking your bets throughout the day.