|Peugeot vende bien en Argentina|
Both of these nations are part of a trade bloc named Mercosur. You wouldn't know it looking at the two car markets, such are the differences. I wonder if vehicles are included. Anyway, the basic issue is how each nation deals with cars that are imported. The figures below are for cars and light commercial vehicles. The ratio difference is 1: 5.1 so brands with a ration under 5.1 are more popular in Argentina (blue) and over that in Brazil (yellow).
Starting with Brazil, the big selling makes are made in the country. By looking down the Brazil column it becomes apparent who manufactures cars there. Those that import do so in limited numbers, such as Chinese brands.
Argentina is different because while again the big selling brands are also made there, those that don't make any scarcely exist in that nation - if at all. An increase in import duties in recent times has devastated makes such as Suzuki. It keeps most Chinese brands out also.
However Chery is more popular in Argentina than Brazil, perhaps the lack of other brands from China assisting in that. Still, sales for Chery dropped over 50% in 2014 as increased import duty did some damage. French brands are well liked in Argentina while Asian ones are more successful further north. VW is about even.
The contrast is greater in the premium sector, where nearly all marques sell better in Brazil. I have left off some small selling brands in Brazil that don't even feature in Argentina. Mercedes probably does well in the Argentine because it is the only premium marque that makes cars there and the others that import cannot compete, ensuring market dominance to MB. BMW sales fell 85% in 2014 and Land Rover 72%.