Well, my opinion is opposite.
I think Argentineans are a good resource for them as most of my friends flying in my country have been interviewed by COPA. If they wouldn't like them, they wouldn't call them and hire them.
With brazilians, they have language issues. Most of them don't speak spanish well. They have B737 experience because of Gol and Webjet but speak portunhol or a very basic english.
The rest of latin america is not a good place to find a < 30 yrs with multi/jet experience, OACI >= 5. (Which is not what they require but I'm sure they appreciate).
But at the end it's a about completing their process well and not what they like or dislike.