As a AAdvantage member I'd like to share my experience too.
I've looked into the LATAM program and its revenue-based model is much different than what AA provides, the first requirement being that you have to fly a certain number of premium cabins on LATAM each year to qualify for anything meaningful (Platinum/oneworld Sapphire and above). Depending on your airline preferences, this may or may not be very easy for you to attain.
In AA's revenue model, if you fly partners you can get EQDs (Elite Qualifying Dollars) at a percentage of your flown miles. The EQDs is harder to earn on AA code as it only counts base fare + YQ/YR, but if you fly mostly partner airlines like I do, a few runs on CX Premium Economy, etc. very good routes for EQD (e.g. LATAM IPC-SCL) the EQDs are no problem at all to attain.
I'm not sure whether LATAM allows accruing "Elite Dollars" on non-LATAM flights, so I cannot comment on these.
If you often fly in North America (pure domestic itinerary), note that AAdv will not provide you with lounge access, whereas other carriers' oneworld Sapphire/Emerald will.
If you often fly Y on LATAM you can try and get upgrades using the coupons every year, but I am not sure about the upgrade odds too. On AA, you're only going to get decent changes for domestic complimentary upgrades if you're Executive Platinum/Emerald if you fly busy routes. No upgrades on int'l flights, except Emerald which gets 4 one-way systemwide upgrades per year, which is valid for up to 3 segments one-way on AA metal.