As stated above, you can only book WDTC AAA packages through AAA. Room only you can book using AAA through Disney or DU, or whomever.
Using Disney vs. any TA (including AAA) depends on you.
Anyone you book through, other than Disney, "own" the reservation. Even if you have it paid off or not. The only thing you can do on your own is make ADRs. (Or the TA can do it for you too of course.)
Some people run into issues with not being able to make their own changes on a res, and that it has to go through the TA. Some it would never impact.
So one downside is the TA owns the res and you really don't have control over it. If you want to make a change, and the TA is on vacation, they are closed for the weekend, etc, then you may be frustrated.
Depends on if you like the control, or if you want to just tell someone what you want and let them do the legwork and earn their $.
