Difficult to compare because most people only do a master’s at one university and the background/goals matter, too. However, my take is:

The CS department at UPB is separates in four pillars:

1) Software Engineering,

2) System and Embedded Software,

3) Theoretical CS,

4) Human-Computer  Interaction (HCI).

The master’s is structured into modulus of two related courses. The student chooses a specialization area from the four pillars. Then the student takes 1 module from each of the other pillars, 3 modules within the specialization area, a one-year research group project (which is critically important) in the specialization area, and the master’s thesis (usually, but not necessarily within the specialization). Within the course modules there is usually a some choice of concrete lectures to take. For German standards, the professor body is pretty large (21 research groups). That means a good choice of fields and sufficient number of lectures. How research-y and difficult the project group and the master’s thesis are depend on the student and the group, but range from “barely” to “highly”.

From my point of view, the theoretical CS department is very good. Highly esteemed professors that do good teaching (Blömer, MadH, Scheidler, …). That department usually attracts the best students in each year. There are exceptions, but I would say that 8 of the 10 best students specialize in that department. The systems department is with Platzner, Plessl, and Karl, … equally good. The engineering department is very proud of themselves and let’s stop speaking about them. I never had much insight into the HCI department. It is an interesting and important topic, but I never liked their teaching much. There is the Heinz Nixdorf Institute in Paderborn that works closely with the university. You will find an excellent teaching and research environment there.

Depending on the courses, specialization area, and research group, and your goals, you can get an excellent CS eduction in Paderborn or an easy way through without much work (usually not both at the same time). For systems and theoretical oriented students, the master’s in Paderborn is in my opinion pretty good.

The university guarantees that it is possible to do the master’s in English. However, that means that the lecture choices are a bit more limited as some courses are only given in German.

The master’s may have two problems:
– Changing universities is not so common in Germany. People stay where they started their bachelor. The master’s thus has been designed with the UPB CS bachelor in mind. There may be pitfalls when transferring. However, this is a guess. I don’t know of anything concrete.
– UPB CS has the general tendency to see anything programming/coding related as grunt work below of the Gentlemen status of a UPB graduate. You may go through the master’s without a single LOC. The current dean of the University, a professor from the Software Engineering pillar said in a lecture “All programmers are dump”. That is absurd.

Job prospects: There are a number of CS companies around Paderborn. Usually in the automative and embedded programming space (the economy of Germany is essentially car-related), e.g. dSPACE or HELLA. These companies collaborate closely with the university. If you are interested in that space, it is usually possible to create connections with them during the master’s and e.g. do a practical master’s thesis with them that directly can lead to a job offer. However, these master’s thesis usually have a scientific value of 0. The software engineering department trains students with the goal of them becoming consultants. Locally, the job prospects depend on the groups and courses you take, e.g. the local companies now pretty well which courses don’t require any work. If you send them a resume with only these courses they will notice. Internationally: I know a good group of UPB alumni working in Silicon Valley (startups, Google, in between).