Over my lifetime, each country has had its share of bad leaders, so I'm not going to vote based on the political landscape of 2021. I have been to Brazil, but not Argentina, though I have worked closely with colleagues from both and would probably enjoy more time in either culture. However while in Brazil I loved Florianopolis with its blended European and South American character. So that sways my vote.
I you went to Floripa during the (south hemisphere) summer you've already visited Argentina
It was Nov 3, 1994 to see the total eclipse of the sun. That in turn was a side trip during a 9-day visit with colleagues in Rio.