I suggest you go for Asp.net MVC and never look back to Web form again The point is it doesn't necessarily mean that you cannot develop the same kind of application in web form that you can in Asp.net MVC but the ease and flexibility and of course testable from the ground up that Asp.net MVC has to offer is not comparable to Web form development. Start on some professional Asp.net MVC book and get your hands dirty developing some small application and moving all the way up to professional and more sophisticated application that deals with OAuth and various aspect of the application you are trying to develop.
Asp.net MVC is getting better.....