I know , you have to see the falls from both sides of Brazil and Argentina to enjoy it . My dad said that the Argentina side allows you to expieriance the falls while the Brazil side allows you to appreciate the beauty of the falls
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.