I'm not a macroeconomist, so I can't comment on that. But I will say that you should probably not be choosing based on the size of the stipend. The differences are small relative to your lifetime income and relative to the importance of so many other factors. Look for a department that has a good group of faculty and graduate students working in macro. Talk to the students about what they like about the department, what they don't like, etc. Do they feel supported and mentored? No one else can tell you which is a good fit for you.