Medium! And I know, what you now say ... but I don't like rare or so.

I suspect, the Argentinean beef is NOT aged.

Like at Peter Lugar:

"....the loin is brought back to the premises of the restaurant where the dry aging process begins.

The loins of beef sit in a temperature controlled cooler where air circulates around them. After the meat is properly aged, it is butchered and brought up to the kitchen for broiling..."

La Brigada San Telmo: NO! I am not a fan of San Telmo .. somewhat touristy and doesn't look clean, sorry about this.

However, we have been at La Cabrera and liked it a lot. Difficult to get a place.

Beware of La Cabaņa:
High prices, unfriendly service, lousy food. Other than this place, we where NEVER disappointed in BA.

I learned from El Establo on your forum (the story with fake money):
We liked it. It's somewhat plain, but the food and the service was perfect.
On our way to the restaurant we recognized a young couple with a little baby, homeless .. sitting on the steps of a closed shop. We got a doggy-back and delivered it with some pesos on our way back.