Well, I've stayed at all of the Epcot resorts, and generally spend a couple trips at BC/BCV and a couple BWI/BWV each year.
I prefer BC/BCV when the weather is warmer, because it's so close to Epcot (my favorite park). When I stay there, I typically walk to the Epcot boat dock instead of walking to YC to catch the boat to DHS - the distance feels about the same and I can usually get a seat getting on the boat at Epcot. The small balcony situation doesn't generally come into play because it's too hot to enjoy a balcony when I stay there anyway.
To be honest, I prefer YC to BC/BCV, but since I only book if I can get a discount, the discounts seem to be a little less frequent at YC. You don't have the small balcony situation to deal with, the boat dock is right off the lobby, and you can still use SAB.
When the weather is cooler and I'm more inclined to walk to both parks, the BWI/BWV location works out better. It also feels like there is more to do at the resort itself, and more dining options right at my resort, when I stay there. I also enjoy the balcony on the room because I stay there when the weather is cooler.
I agree that if you drive, the parking at BC is much closer. But if you are flying and using ME, the parking situation won't be a factor in your decision. I don't have a preference one way or the other as far as pools, as I'm not a big fan of public pools in general.
I don't think you can make a wrong choice between them - just look at the amenities and see which is better for your family.
