We are a family of 4, so I cannot comment on room sizes for your family of 5, but the first thing I'd do in your shoes is to consider the above advice regarding room size and figure out if one resort benefits over the other in that regard.
As far as the resorts themselves, keep in mind that they are only a 5 minute walk away from each other, so if you stay at one, you can easily walk to the other. So if you stay at BC, you can walk to the boardwalk for the nightly entertainment or to rent surrey bikes, ESPN Club, dancing, restaurants, shopping, etc. Eating -- technically no "fast-food" food court at these resorts, but you have 100's of options right within walking distance. BC has the Marketplace with fast-food items to choose from and also Hurricane Hannahs at the pool with the typical choices. Also Beaches & Cream, a 50's type restaurant. Then there are all the options on the boardwalk and also all the Epcot countries. On the boardwalk, there are food stands set up, pizza take-out window and you can order by the slice and sit outside and eat, etc.
Which resort would WE choose? BC. We love the sandy-bottom pool area for our toddlers. And we love having a character breakfast right in the lobby. And it is the closest resort to Epcot countries. And we can walk to the boardwalk each night for some entertainment. We love it there.