Porcão has closed. If it opens again, avoid it at all cost. It has become a zombie in bankruptcy.
If you must try a Southern Brazilian BBQ, then go for Fogo de Chão, but its buffet is quite disappointing. If you would like to try one with a buffet that mirrors the old Porcão, then prefer Churrascaria Palace or even Carretão.
If you'd like to try Rio-style BBQ, then go for either Braseiro da Gávea or Filé de Ouro.
Avoid Filé de Ouro in the evenings, I only recommend it for lunch.
Braseiro da Gávea is always terribly overcrowded, so arrive at noon sharp if you'd like to avoid waiting on the curb.