Remember reading some analysis back in the day that the Chileans were considered a tough professional army whereas the Argies except for the Mountain brigades were rubbish.
Pure propagandistic by Pinochet regime...Chile was, as well as Argentina, a conscript Army. Argentina had very good mountain troops, as well as marines, and the advantage, if we caln call this a one - comparing to Falklands-Malvinas war- was that the conscripts were training all the year for an incoming war. The "political" army was a Chilean issue as well, as Chile was ruled by a Dictatorship as earlier as 3 years before Argentina. And Chile was not self enough to supply themselves in light weaponery not even heavy. Argentina had a large military industry complex at that time.
As I put in another forum
The chilean submarine Simpson was found and pictured by Santago del Estero submarine as you can google it. Chile had in service only that old guppy class submarine because the other three had problems. In fact chilean fleet had passed over ARA Santa Fe, when both fleets mobilized to war. Argentina had two new at that time U209 subs and two guppy class in the zone
In Tanks, all argentinian Shermans were modernised by 1977 with 105mm guns , radios and other stuff, like Israel did it. AMX 13 tanks, SK105 KURASSIER and Full production of 155 mm artillery And TAM tanks were in pre production. Chile had Shermans but from post WW2, and M 24 and a few M41.
In troops, both armies were conscripted based army, but in Argentina' s case, they were training for that and called reserves overnumbered 500.000 men. Of course Chile had its plans and were training. Chile had a half of Argentina' s military budget and Argentina GDP was almost four times than Chile.
And Chile had troops in north because of a fear of a Peruvian attack.
Main problem for Chile was that once war started, they will be lacking of oil because of embargoes and the few refineríes were in south and targeted by Arg Air Force. Chile was not self sufficient in infantry weapons at that time as Argentina and worse for oil and trucks
Argentina had its 25 de Mayo CV at its full and despite chilean rumours, the carrier was in conditions after an overrun made in 1977.
In Air power CHILE DID NOT HAVE MIRAGE! they came after 1981 and the F5 were not all availabe because of Humphrey Kennedy embargo. The same problems with their Sidewinder AA missiles. Same happened with Hawker Hunter aircraft, because UK embargoed Chile , yes, you read right. In fact UK sold Argentina at that time ships (ARA HERCULES and Santísima Trinidad, both T 42 like Sheffield) , missiles like blowpipe and other things...as you can see, UK didnt see Falklands as a problem.
And you forgot to mention Argentina had Canberra bombers. But yes, a bombardment made by Argentina would not be considered a heavy one for an extended front.
Main powers did not have problems to sell weapons to Argentina and put a huge embargo to Chile because of human rights. At that time Chile had a worse international image that Argentina, and you can see it when France did not sell two A69 ships to South Africa and inmediately sold to Argentina in that 1978
It would be an Argentina' s victory, but to a cost that would not justify a war. Worst will be for Chile.
Chile was ruled by military hand so they were actually involved in political affairs. So they were distracted in internal matters as well. It is true that Chile had one lead voice, Pinochet, while in Argentina were three or more in some times.
About DINA poisoning water, I assumed that (of course is my opinion) as part of dissinformation and propaganda. If you see the Planta Potabilizadora Gral San Martin, is HUGE, so with water in movement, you have to put millons of m3 of poison, and how can you do that without not being alerted?
If that plan succeed, international image of Chile would fall to pieces and say farewell to see even a screw from outside. And must remember that Argentina at that time had a developing nuclear investigation, more than Brazil at that time, so arg militaries could use to build some "dirty bombs " as retaliation.
At sea, I see a pyrric victory, Argentina would win for, let say, 5 o 6 chilean ships sunk for 3 argentinian sunk and others damaged for both. Chile remained badly injured but enough to avoid Argentinian fleet to cross freely to Pacific Ocean.
Plans for Argentina were aproppiate of disputed Islands , chilean side of Tierra del Fuego, some southern territories close Santa Cruz province, and destroy civilian and military infrastructure but not a full occupation. The destruction was in order to avoid Chile "would be able to be a threat for 100 years " as exaggerated an officer many years ago.
Glory would allow Argentina' s military to give up power in better shape than OTL, but not many years more. Despite all, as Peron said, for argentinians "la fibra más sensible es el.bolsillo "...(
the most sensitive fiber is the pocket)
By 1978 in Argentina, Montoneros were defeated, but in their platform said that they would not intervene in the "imperialist made war " but if there were attacks into Argentina' s territory, they will defend argentinian soil
For Chile, recovery will be harder but eventually will recover their economy. As you can see on earthquakes in 2010, Chile had a tremendous capacity of reconstruction
The World would not care after they'll finish. Chile would ask for China, Argentina for USSR in UN Council Security, for any veto that guarantee argentinian territorial progress at least for the first 10 days of war (this according to historian Rosendo Fraga, that General Viola, when went to Moscow asked for that) Argentina had excellent relations with USSR but not a degree to buy them weapons, except if war went wrong.
US will extent their embargo, Brazil would be happy to sell weapons to Chile, because they don't want an hegemonic Argentina but they don't want three atlantic powers, that was their game. West Germany, France and Israel over all, would talk about peace but will still going on their business on selling....specially to Argentina. After all , with their weapons levels, this war might not last more than 40 days. If Guerilla ops appeared they would not require to sell heavy weapons.
Of Course Carter will be accused again of weakness because, the blockade could be vulnerate and then Argentina, to congraciate , will send officials to Central America as they did in OTL.
But when this war would be over, no one at Central Powers, is going to care about.