I think that the Junta invaded for their own domestic reasons, they needed a diversion and the Malvinas provided it. Their assesment of British capabilities strikes me as justification after this decision had been made, and what's more made after their assesment of British intentions. The Junta's thought process in my mind was something like this; 'We're under the pump lets invade the Malvinas and be popular, the British don't want them and won't do anything, and besides they can't anyway'.
If the Ark Royal had undertaken one more refit and commision the thought process would be; 'We're under the pump lets invade the Malvinas and be popular, the British don't want them and won't do anything, so that old worn-out carrier won't matter and besides it will break down anyway'.
However in reality the Ark would go south, and make the tone of the war somewhat different. I think the close support that GR3 Harriers provided would not occur, Buccaneers would be tasked with bombing the shit out of everything. They would also be used extansively as buddy tankers, and I think it would be they who would sink the Belgrano. The land war would go more quickly because Hermes would be used as a Commando carrier and the land forces would have many more helicopters and perhaps a Chinook or two from the first day. The AEW and tanker supported Phantoms would probably get wired for Sky Flash and 9L on the way south and get a large number of air to air kills, maybe produce an ace. On the whole I think the entire campaign would be conducted with a lot more confidence than IOTL.
