My take on it
I needed to get tickets for this summer AEP-MDZ-AEP/EZE-GRU.
So called AA RTW desk and quoted me the fare which was at a 10% discount.
Also called LAN and asked to get a quote for the same flights. In turns out that the LAN south american pass was cheaper in Taxes plus it was a higher fare class (H) than the one world south american pass. ^
My 2 cents is do your homework and shop around.