Best steak recently for me has been a ribeye at Del Fisco's in Dallas [north].
As for the Argentine beef, it is good. However, I have found the Uruguayan beef to be better, quality is the same, however I found the restaurants in Montevideo to have much better preparation and service, and without the porteņo snobbery

. Montevideo is also very clean. It is a smaller version of BA, and just as cosmo, me thinks.
Punta del Este beach resort is just a few hours drive, and also enjoyable in season.
Z