its opinion really, personally I think the AoW missions were much more creative then Generals, but they are slower if you don't know how to play it properly.
As far as I know, AAOWA isn't moddable... you can only create maps. But then again I havn't checked the news for a couple months. I bought the game and I loved the overall "feel" of it, it felt much better than generals. But the lack of modability really shortened that games' life on my computer.