Are the chances of getting a postdoc position or full academic position higher in the country you are going to study your PhD in? What if you are not a citizen? Is it important to take into account postdoc stage and career path possibilities when you decide the country you want to study PhD?
In my surroundings (Germany, Switzerland), normally it's not a problem to get the first postdoc after you get a PhD in the same country.
However, a PhD in some country that is (sometimes wrongly) believed to have an inferior level of scientific merit may actually block the further scientific degree carrier abroad: impossible to start PhD studies a second time ("already has PhD"), and impossible to get a postdoctoral position as well ("bad PhD").
As a result, it is important to weigh the situation and think where and how to earn the PhD degree. I know people who have dropped basically complete PhD works right before defence just to be able to restart in another country.