Huh? Add a handful of lines of code in your iOS/Mac app to add another login button or implement a whole server based authentication scheme? Maintain and keep

Huh? Add a handful of lines of code in your iOS/Mac app to add another login button or implement a whole server based authentication scheme? Maintain and keep secure the server based authentication for the lifetime of your app? That is not at all likely given the relative cost in money and time between the two choices.