Since I wouldn't know who of the regular members here should be able to help you on this (CharonY, perhaps), I'll give you a few bullet point comments. Keep in mind that while I have been formally employed at a Max Planck institute last year (not the one you are interested in, though), my knowledge stems almost exclusively from experience at my current university (where we have some collaborations with local MPIs - which is why I was paid from them).
- Max Plack Institutes have a good reputation in research.
- Students from MPIs are notoriously bad speakers and terrific teachers.
- That is -presumably- because their supervisors push them into doing the lab-rat work rather than wasting their time with giving yearly progress reports and tutoring university students.
- Pressure on PhD student in MPIs tends to be a bit higher than in German universities, but no where close to the horror stories one hears about being a PhD student in US universities.
- Leipzig should be relatively inexpensive to live in.
- The good looking women usually get on and off the train in Leipzig

- People having lived there tend to say the city is nice (may be related to either of the previous points)
- I have no clue about the particular MPI you are looking into, never even heard of it (but I'm not into neuroscience, so that doesn't say much)
- Same for the Neuroscience Center of Zurich
- You may be interested in this link:
http://www.nncn.de/ (but it may also be inapplicable - "cognitive" is a buzzword to me).