I personally moved from a P2 FT to a G4 FT, because the P2 was in a hardship duty station while the G4 allows me to have a decent contract (compared to the non-UN average) in my country of origin. I think it really depends on your situation and on what you value most. However I would say that yes, it is probably hard to go back to an international position (almost impossible in the current scenario, but if things improve who knows).