My opinion is kinda similar to your dad's, I think in the brazilian side you see a natural-point of view of the falls. Also, there are a lot of coatí asking you for food
"Give me food! I'm cute!"
The argentinian side, as your dad said, is an amazing experience to "live" the falls.
There is this elevator in Brazil that shows you the full falls . Thats when my dad realized that Niagara is way way behind this . He thought they looked similar until then