I live in California, visit Canqda quite a lot and have been to Buenos Aires three times. Without a dout, the steaks to get in Argentina are better by far than anything I can afford in California and certainly better than anything I've ever had in Canada (even at the hights end restaurants in BC). Personally, I'd take the US beef over Canadian anytime and Argentine over US.

Of course the best way to figure this out is to book a quick trip to BA, stay in Recoleta and eat lomo everyday, along with a nice bottle of Malbec.