I am a native speaker of Dutch and proficient in English. My German reading and understanding is quite good, since I had German in high school, but speaking had regressed to a 'can manage at the bakery'-level ;).
Both groups I worked in had a fair amount of people who couldn't speak Dutch/German --- for research it's definitely not a problem. In teaching it seems that The Netherlands (and probably Scandinavian countries) is more flexible: non-native speakers are typically allowed to teach in English. In Germany, this seems more problematic unless it's an international program.
Outside work, I would definitely recommend expats in Germany to learn German. Most Germans are not really proficient in English (not even general practitioners). In The Netherlands you could easily survive without knowing Dutch.
Both groups I worked in had a fair amount of people who couldn't speak Dutch/German --- for research it's definitely not a problem. In teaching it seems that The Netherlands (and probably Scandinavian countries) is more flexible: non-native speakers are typically allowed to teach in English. In Germany, this seems more problematic unless it's an international program.
Outside work, I would definitely recommend expats in Germany to learn German. Most Germans are not really proficient in English (not even general practitioners). In The Netherlands you could easily survive without knowing Dutch.