Even buying JF-17 Block 2 would be a great choice, I feel if they manage to buy, Block 2 Thunder will be a sufficient aircraft to tackle with and also a cheaper option against modern aircraft. Though Chinese would push their own aircraft to Argentina for a direct deal.
Personally i feel buying Kfirs wouldn't help them a lot, as their adversaries will be flying damn advanced aircraft against their Kfirs, So better they wait and buy some numbers of Chinese advanced aircraft.
Not really, Kfirs are old but will undergone a massive upgradation plan in Israel before flown to Argentina, and upgrading old aircraft to new standards is also very money consuming, so the Kfirs deals is not gonna that cheap that some are thinking.