I traveled to both Rio and BA in Feb 2020. It was my third visit to Buenos Aires. I find Buenos Aires to be much more tamer than Rio, however BA is more cosmopolitan than Rio, which is a more back city with a beach culture. Both are great cities to visit.
I stayed at the Arc Arenales (apt/hotel) just on the outskirts of Recoleta, but in a quiet, residential area close and was very pleased with the accommodations. Large space, with good internet, quiet building, with a kitchen, & a nice sized patio facing the courtyard. Secure, modern building with a 24 hour front desk and a great value.
Also, when exchanging currency (dollars to pesos) you will get a much better rate using the 'blue rate'. I exchanged dollars at a Western Union and a local cambio, and also at my hotel, for a much better exchange than the official rate.