The faculties of some German universities offer a choice of doctoral degrees. For example, Technische Universität Darmstadt's Department of Computer Science allows candidates to apply for either a Doktor-Ingenieur (Dr.-Ing.) or a Doctor rerum naturalium (Dr. rer. nat.). Candidates choose which degree they want to apply for shortly before they submit and defend their thesis; the only guidance provided is as follows:
Der Dr.-Ing. wird im allgemeinen auf Grund einer Dissertation verliehen, die überwiegend ingenieurwissenschaftliche Erkenntnisse aus der Informatik enthält.
Der Dr. rer. nat. wird im allgemeinen auf Grund einer Dissertation verliehen, die überwiegend theoretische wissenschaftliche Erkenntnisse aus der Informatik enthält.
The Dr.-Ing. degree is generally awarded on the basis of a thesis that contains predominantly engineering-related findings in computer science.
The Dr. rer. nat. degree is generally awarded on the basis of a thesis that contains predominantly theoretical scientific findings in computer science.
Other German universities may offer yet other degrees. I know some computer scientists who hold a Dr. phil. (Doktor der Philosophie).
In some cases where the university offers various doctoral degrees, a thesis may meet the criteria for several of them. (For example, in the TU Darmstadt example, the thesis may contain engineering-related and theorical scientific findings in roughly equal proportions.) In such cases, is there any reason for the candidate to prefer requesting one degree over the other? Do the various computer science degrees have different standings or reputations? Will having one or another make it easier or harder to get certain types of jobs in academia or industry, either in Germany or abroad?