^Even without del Potro, Argentina is the favourite. They have more depth and better ranked players. Brazil has the edge on the doubles, as we have two top ten doubles players which used to play together.
Right now the top ranked braz. is no longer Bellucci (as above), but João Souza, who had two good tornaments in São Paulo and Rio. Bellucci, however, is able to wake up one day and have the match of his life, no matter where he is ranked. Put it all together and Argentina is still the favourite (and who knows what they can do once del Potro returns), but Brazil has a shot.