It depends so much on the child, the school and on how you feel about it.
My father worked outside the UK for all but 2 years of my schooling. I did a glorious mixture of local convent school, local British army schools (day and boarding), local international school (boarding)and finally a girls' public school in the UK. I boarded from 11. Looking back on it, I quite enjoyed the boarding, and went to some extraordinarily good schools. (My much younger sister boarded from 8, and had a much tougher time of it.) It helped that my grandparents were incredibly supportive, as were my uncle and his wife.
My mother found it incredibly hard to have us away at school, but my parents seemed to be in agreement that they were doing their very best to get us a good eduction, and certainly my father turned down jobs in the UK which would not have paid enough to support three daughters at boarding school.
Now, they live a longish way from their original home town, I live at the far end of the country and my two sisters live in the USA and Australia. We are all three of us pretty rootless.
I find that now, making decisions about school for my son, I am probably more hung up about stability and local roots than I am about boarding as such. If I were living overseas and likely to stay put, I would probably opt for the local international school (but with all the caveats about where he will then consider to be 'home') If I were likely to keep moving around, I would look very hard for a boarding school in or close to our home town so that my son developed some roots.