I want to eventually work in string theory and QFT integrability. I did my Bachelor at the top university in my country, and wrote a research level paper as my final project (wasn't published, but the results were non-trivial). My supervisor was a pretty big name in the field as were two other professors. I'm currently doing my Masters at a well respected European institution (DESY). I will be doing my Masters thesis under another one of the hotshots in the field. For my PhD I would like to return to my home institution and work with one of the other professors, one of whom is incredibly close to my Masters supervisor (they write nearly all of their papers together). He has previously expressed his willingness to work with me. However, would it be more beneficial for my career to go to another institution which does a lot of work in the field? I can imagine it would be better since I'd learn from a larger group of people, but would it be detremental to return to my home university?