I did LAX-PTY-EZE last year in Clase Ejecutiva. Service was great, but both segments were really long for a 737. Going south, it wasn't quite as bad: red-eye from LAX, and then down to EZE in the morning. Northbound wasn't so nice, though: two 7+ hour flights that day. I don't even want to think about what that must have been like back in coach. A bigger plane definitely makes a difference on long flights.