Both can be pretty bad (T7: imagine a BA 747 unloading 30 minutes after a CX 77W and IB 346 arrive) but both can also be excellent as well.

If I needed to make a blind bet (because of a connection or something), I'd probably go for AA since the queues are generally a bit longer but the terminal also absorbs tons of people a lot better, so it's a bit more normalized (T7 can be a bit extreme at the worst times).