I'm bumping this thread because I have the same question. I usually buy whatever crema I find or the one that's on sale, but I think I prefer the Salvadoran style. It seems a bit tangier and sweeter than Mexican crema.
Does anyone have more info on the differences between these styles?
Crema Mexicana is milder & more fresh-tasting and has the consistency of crème fraîche.
Crema Mexicana agria is a more acidic, thicker version of crema Mexicana.
Crema Salvadoreña is thicker & tangier than Mexicana with the consistency of sour cream.
Crema Centroamericana is sweeter & thicker than Mexicana.
Crema media is similar to whipping cream.
I often see the brands Cacique and El Mexicano/Marquez Bros. here in California. They label their products a bit differently from each other.
What Cacique calls "Crema Mexicana" ("Mild and buttery, very fresh milk flavor, rich luxurious mouthfeel" according to their website) is called "Crema Fresca Casera" by El Mexicano. Both containers say "Grade A Table Cream" on the label.
Cacique: Crema Mexicana Agria ("Truly full flavored, tangy and savory, rich mouthfeel.")
El Mexicano: Crema Mexicana
Label on both: Grade A Sour Cream
Cacique describes Crema Salvadorena as "Tangy sour cream flavor and creamy mouthfeel."
Marquez describes it as "acidified sour cream".
Marquez Brothers lists the following products under sour cream: El Huache Crema Mexicana Natural, El Mexicano Crema Mexicana, Rancho Grande Crema Mexicana
as Acidified Sour Cream: Crema Salvadorena, Crema Centroamericano, El Mexicano Crema Favorita, El Huache Crema Mexicana Agria
as Table Cream: Crema Fresca Casera & Crema Superior (El Mexicano), La Michoacana Crema Mexicana
So even the same parent company can confuse us since their "La Michoacana" Crema Mexicana is a table cream but their "El Huache", "El Mexicano", and "Rancho Grande" lines of Crema Mexicana are sour creams.
I use Crema Mexicana for most applications. It performs as crème fraiche does by not falling apart when heated, so if I'm not up to making up a batch of that (or if there just isn't time) I'll go buy the crema. I like it drizzled on green-chile omelets or whatever with a drool of Pico Pica … I've tried several of the different ones, but their relative characteristics vary so much from brand to brand. I've been buying them for over ten years now and I'm still not exactly sure of all the differences. Too bad they don't sell tiny sample bottles - the only reason I haven't gotten one of each to taste is the waste involved, since we don't use gallons or even pints of this kind of thing.