For such a long trip, you are better off with LAN. They have larger planes and very decent service. My experiences with LAN so far have been great. They are very image conscious and respond positively to customer feedback / complaints etc., especially if you are North American. Whenever I had a choice between TACA and LAN, TACA seemed to have the more expensive tickets, and odd flight times and connections. LAN cover pretty much all of South America and has good connections all over. Hope this helps.