What is unique to Ratzinger's theological methodology is, in the first place, its originality and creativity. Despite all the influences I mentioned, Ratzinger retained his distance and so retained his independence as a thinker, even with regard to the great theologians he studied.
His methodology is to take as his starting point contemporary developments in society and culture, then he listens to the solutions offered my his fellow theologians before returning to a critical examination of Scripture and Tradition for pointers to a solution. He is not satisfied to analyze a topic, but, having dissected the issue, he then attempts a systematic answer by seeing the topic in the context of theology as a whole. Unlike Küng, who is always in tune with the latest fashion, Ratzinger is not afraid to be unfashionable. Unlike Rahner, who produced a full systematic theology, Ratzinger's theology is fragmentary--filled with brilliant insights into almost every subject of theology and yet not a fixed "system".
Using the best findings of academic theology, Ratzinger goes beyond them to create something new and original. He is more than an academic. He is an original thinker, whose scattered writings on a host of subjects are "seminal", awaiting development by others. Finally, unlike either Küng or (especially) Rahner, Ratzinger writes with a clarity and, at times, literary beauty, that never fails to impress.