I could do this then:
Saturday EWR to GIG - land Sunday afternoon
Monday: Rio
Tuesday: Rio
Wednesday: Early flight to IGU, half day tour of Brazil side
Thursday: Iguazu Argentina side, evening flight to Buenos Aires
Friday: Buenos Aires
Saturday: Buenos Aires
Sunday: Buenos Aires, fly home on late night flight
The downside to this is in order to take an early flight to IGU, I need to pay for it but it's only $90, so I think I can handle that. The free flight that's available through United doesn't get in until later in the day and I would rather have more time to see Iguazu.
Is that really enough time to see the major highlights of each place?