My experiences have been the opposite...I am always amazed at how rude and entitled the other passengers on the EZE flight to/from the US behave (I've flown the DFW, MIA, and JFK flights). The only time I've had a pleasant experience flying here was on a flight from MIA to MVD. I asked the attendant if the flights are always like this compared with EZE, and she said it's a dream for them and the other flight attendant agreed stating she'd take any other flight to South America over EZE. I'm dreading getting on my next flight just thinking about it, now. Ugh.
I agree that passengers on flights to BA are louder and take longer to get settled than on other flights I've been on. They tend to stay in the aisles too long and have a lot of poorly behaved children.