I don't know why you want to avoid US carriers. One other choice that you didn't mention, that I think is valid, is Copa. LAX-PTY-EZE. I have flown this, and while on a 737, their business class was acceptable.

Personally I prefer to fly CO in Biz class. I've flown DL in Biz, and I didn't like it much. I flew on AA once, and it was okay, as well. I've booked MX awards before, but a CO flight always came up later, so I switched to that.

Of the other ones you mentioned, I have taken LAN to South America, in Biz, and thought their service was fine. I haven't flown them into EZE, yet.