As a Scot living in Argentina I would say yes Argentine beef is good but not always. You can still get a poor bit of beef on the odd occasion from the butchers so it's not a certainty it'll always be tender.The way of cooking it here over the embers of burnt wood rather than charcoal definitely makes a difference to the taste no doubt about it.
Of course being a Scot I have to put a good word in for Scottish beef and it's no coincidence that a fair percentage of Argentine beef comes from the Aberdeen Angus breed of cattle.