I think LAN are now doing that route direct with 787´s - that would be nice in J!! Not sure availability redeeming AA miles though.
I for one absolutely value the lounge access in Santiago. LAN has great red wines, cheeses, and good other snacks. I suffer 12hr stopovers in SCL whenever I come over from Australia, heading through there to Colombia. Aussies have to pay a huge reciprocicity fee if they want to leave the airport, so I happily spend that time in the lounge there instead. There is a small área with some day beds that you can have a nap too. And usually in the afternoon they have good sushi. So really it depends a bit on your tastes and how much time you will be in the airport.