If you want to understand the dynamic of why one store is cheaper than another, you have to understand the battles/collusion that pervade in the Argentine market.
For example, Carrefour owns Día (Groupe Carrefour), and Jumbo owns Disco and Vea (Grupo Cencosud from Chile). And Coto (Arg) and Wal-Mart (US) (AFAIK) only open markets under their own names. Meanwhile the Chinos are independent in name only; most of them are not only members of an association that regulates prices and supply chains, but (rumour has it) they are also very dependant on the same mafia-like network to provide the titular owners that run the stores.
So you mainly have five players in the market:
1. Carrefour/Día/Norte
2. Cencosud/Jumbo/Disco/Vea/Easy
3. Coto
4. Wal-Mart
5. Chinos
While there is certainly a history of animosity between the Chinos and the big market chains, recent years have shown suspiciously close pricing, and this was only solidified by all of them voluntarily acceding to the Precios Cuidados scheme.
Personally, we only set foot in one of the big chains on days when they have deep discounts, and I'm not wealthy enough to
evenbreathe the air in Jumbo.