I did this route with LAN (although the first leg was with Iberia – you can check bag right through of course).
I was very impressed with LAN business class and slept very well (7 or 8 hours out of the 13!) on the flat bed. It is a fully flat bed and the food was very good too.
I have not flown Iberia so I cannot say which is best but LAN was not a disappointment!