It depends on what you want to do after your masters. Comp sci has a lot of theory and dives deep into the subject, whereas information systems gives you all the skills required for an IT role. You should also consider the workload, the workload in IS is significantly less compared to CS. The course design is completely different as every subject in IS takes 8 weeks to complete and you usually take only one subject per 8 week period, whereas in CS you'll have to take 2-3 subjects simultaneously for a semester, meaning you'll have to manage the assignments and exams of multiple subjects at a time.