Upvote:2
I recently came back from a 6 month trip to Argentina where I also visited Iguazu falls. I only stayed on the Argentine side instead of crossing over to the Brazilian side. I will tell you one thing that I didn't see mentioned in the comments. You should add way more time to whatever you plan on doing because it is currently summer in the Southern Hemisphere.
When I visited, it was winter in Argentina/Brazil. Because of that, there were literally no lines. It took everybody in our group about 10-15 minutes to buy their ticket and enter the park. My guide told me that during the summer it can take as long as 2 hours just to enter the park because there are so manny people.
Upvote:2
There are hardly any lines at the border. But when I was going by bus from Brazilian to Argentinian side, and had to step off the bus to get my passport stamped (which took maybe 5 minutes for 10 people), the bus driver did not wait for us. We had to wait for the next bus, which go every 30 minutes.
Then, going from Argentine to Brazilian airport by bus, you have to change to another bus (no. 120, direction "Parque Nacional"), and reserve about an hour just to get there by bus.