Assuming keeping both isn’t financially viable right now:
Those were the only two servers I could play with a good (and acceptable) ping (39 in Santiago & 51 on Buenos Aires). As a Chilean who doesn’t live in Santiago, for whatever reason, I get a better ping in Miami (185 on average) than in Sao Paulo, Bogota and Queretaro (all of which reach AT LEAST 220).
I think I only get two players from Brazil in Santiago, and their ping is at least above 70. I would see a handful more when Buenos Aires was around. I do believe that server would be a much more active place - I’m tired of waiting minutes just to get ANYONE on ANY queue without sabotaging my ping.

Devuelvan el server de Buenos Aires!