After Argentina captured the Falklands, it sent the wrong kind of force to occupy the islands. It's best trained and equipped troops, who were also from the southern regions and thus accustomed to the South Atlantic weather were left to guard the border with Chile, while very young, poorly equipped and trained conscripts who were from the hotter regions of north and central Argentina were sent to occupy the islands. Leopoldo Galtieri didn't really believe the British would actually send a task force to take back the islands.
It goes without saying that these troops were totally inferior to the British infantrymen, which is a big reason why despite the fact that the number of British troops deployed was not even half the number of Argentine troops, and the Argentines were dug in, they still managed to win all major land battles.
Suppose, however, that Galtieri judged correctly that the British might send their task force from the start. Or, he ordered the conscripts off the islands immediately after it became clear Britain was going to respond and sent them to guard the Chile frontier instead, while sending the best to defend the islands against the British? What would have happened then?
In my opinion, British casualties would have been a lot greater than they were OTL, but they would still have retaken the islands in the end.