L&P_Crear. I can tell you my opinion and experience but can't guarantee any accuracy :=)
!st, I agree with Rich. I always rent from one of the majors not that it probably matters that much. I usually wind up with Avis or Europcar. I always rent using my Am Ex card and waive CDW so between my US insurance and Am Ex I think I'm covered. It is expensive, from $40 to $50US per day to rent an economy or mini car in Argentina, usually through Kayak.com who sends me to Rentalcars.com or HolidayAutos.com. There are very few automatic cars available in Argentina and you will probably pay a lot for that. I almost always get unlimited milage. They do block a large amount of money on your credit card when you rent. I've always received it back when I return the car in good condition. I've never had an accident with a rental car so an't speak to that.
T/