With the new tax regulation, as a U.S. citizen, do you have to pay taxes on tuition and stipends you receive when you do a Ph.D. overseas? (I'd assume so, since overseas income is taxable AFAIK, but I don't really know what the situation is).
Even for the job scenario, you get a tax credit for foreign taxes paid which in most industialized countries would probably neutralize any US tax burden and then some. If the job is in a developing country, I would think the cost of living advantages would make it worth it if you were above the limit.
However, not a CPA or finance pro. I went to grad school abroad and looked into the implications of staying a bit.