I would recommend two nights at the Sheraton Iguazu. Especially if you want to visit the Brazilian side of the falls. There are several trips that you can book in the hotel lobby and as I recall the one I took was called the Great Adventure. A five km drive through the jungle then down a long stairs to the boat ramp where you board the fast boats for a trip up to the falls. You will get wet. If you are there over a full moon they also have night tours during this period. This is the web site for the Argentine Park http://www.iguazuargentina.com/ and this is for the Brazil park http://www.fozdoiguacu.pr.gov.br/turismo/ing/

I would recommend dining at the Iguazu Grand Hotel and Casino, had a fantastic dinner there. Much better than the Sheraton's dinner offerings.

As for Buenos Aires if you really need a chain hotel I would recommend the Sofitel here is a link http://www.sofitel.com/sofitel/fiche...he_hotel.shtml

I think it is far superior to the Marriott, Sheraton or Hilton. Another good one that is medium priced is the Melia Recoleta http://www.solmelia.com/solNew/hotel...digoHotel=5951
Just a year old and great location.

The Marriott is a wonderful hotel but I hate the location, too many tourists in the area and the people who prey on the tourists. Walking down Calle Florida is indeed an experience. You are "attacked" by every merchant along the mall. Throngs of people, but it does feature a rather nice mall, Galleries Pacifico lots of stores and a rather grand building,