As you will already be in Brazil, I would stay on the Brazil side at Iguazu and do a day trip to the Argentine side. It will mean shorter transfers from airport to and from hotel. Try to stay somewhere nearish to the entrance and with swimming pools as the Brazil side of the falls only takes about half a day so it is nice to unwind back at the hotel. When you go to the Argentine side get there very early, it takes a full day to explore. The boat trip into the falls is most spectacular on the Argentine side, don't miss it, and when they tell you to put your cameras and other stuff into the waterproof bag put your shoes in as well.