Definitely the products are different - I say that because there are a lot of people, at least in my experience, who prefer an off-brand. RC is somewhat famous

Definitely the products are different - I say that because there are a lot of people, at least in my experience, who prefer an off-brand. RC is somewhat famous for being a discount soda with a strong following. Given the number of people who have a strong preference between name-brands Coca Cola and Pepsi, if they squared those against the few dozen off-brands would there be another they preferred? In another market space Coca Cola and Pepsi are now the underdog fighting back against National Beverage, a discount manufacturer which managed to sweep the market with their La Croix brand. At the same time their Shasta brand still runs fifty cents a can at the right vending machine and in my opinion isn't that bad. Coca-Cola tends to be better regarded than Pepsi due to their history, while Pepsi more often wins blind comparisons. This consumer preference is famously reversed in the soviet bloc. At the same time Coca Cola's Mr. Pibb is decidedly "off-brand" compared to the smaller Dr Pepper-Snapple group. So I think it's hard to say that there's a clear quality hierarchy with sodas. Rather, they drive strong consumer preference and two brands happen to be the best known and most widely distributed. This is more or less true of a lot of other products as well where there isn't a clear objective measure of quality, it just seems especially noticeable with sodas.