Depends what's most important to you! We have friends who would take additional space over anything else - and you'd have that space at AOA. But we'd take the atmosphere, location, pool, transportation options, etc. of BC over more space. It's just such a different feeling at BC than values or even mods - so relaxed, a nice break from the parks, so convenient to get to DHS and Epcot. We just love the option to walk or boat to two parks and not have to rely on the bus. And SAB is an amazing pool - our boys have always loved it.
As for the differences in theme, I once thought that kids would always prefer the resort with a heavy character theme, but I was wrong! One year for Christmas, we surprised our boys with a WDW trip the following March. At the time, our boys were ages 2, 9 and 10, and they love Toy Story. So we thought they would like All Star Movies and booked there. As we got closer to the trip, we had second thoughts about a value. I'd stayed in a value way before kids, but with kids always mod or deluxe. So when we asked the boys whether they would prefer BC, there was no question for them. They FAR preferred BC and talked about how happy they were with the switch throughout the trip. (And this from a poster with the screen name "pixarmom," which is an indication of how much our boys LOVE Toy Story, Cars, Nemo, etc.!)