Unless I am trying to use codes, I like to use Expedia for TD as well. Especially for J, since I don't think there is anything I can get better from booking directly with AC on a J ticket (itinerary change maybe?).

It's as if you got 4.5% off any flights you book there.

But I think there are some Aeroplan cards that can do better? Isn't there one that gives you something like 2 miles per $ spent on AC.com?

If you redeem at 2cpm or more, that's 4c per $ spent, so 4%+. At 2.25cpm you break even between the two cards.