We always leave Ecuador when Carnviale is taking place. We want to see SA, and this year it was Uruguay, Iguwazu Falls, Buenos Aires. Uruguay was lovely, both Montevideo/Colonia were great, I could live in Colonia! Our tour in Colonia was Private very impressive when one on one!
The Falls are definitely a spectacular sight, however I think that the Argentinian side is much better with the 3 walking tours, Brazil better views but very little walking.