I've stayed at all three and I would say it depends. Are you looking at the villas or a regular room? When my kids were little, I preferred BWI because the pool area is smaller and it was easier to keep up with the kids. Plus you have to exit the pool area for the entrance of the water slide. That was hard for us because our kids are 4 1/2 years apart and we had one that wanted to ride the slide and one that could not. At SAB, you can't wear a life jacket down the slide. Some people say the clown pool at BWI freaks them out, however it didn't affect us at all. At BWI, I've only stayed in the villas and the rooms were very nice, but we were at the far end and had quite the walk to our room.
The BCV are much more compact. We had excellent rooms here. I haven't stayed in them since the refurb, but they look even nicer than before. The lobby of BC is very loud and crazy at times because of Cape May Cafe. My kids like this pool now that they are older. We have also stayed at the YC in regular rooms several times and have enjoyed our stay. This lobby is very quiet and if you are looking for relaxing, I would probably pick this over the BC. My family likes eating breakfast at Captains Grille and you can always just walk in. Depending on when you are going though, YC is currently being refurbished. Honestly, for regular rooms between BC and YC, I always go with whichever one has a better rate.
My family prefers staying at the Epcot resorts and you can't go wrong with any of them. We love being able to walk to two parks or take the boat. We love that you can easily get between the resorts for dining and entertainment on the boardwalk at night.
YC is my favorite of all onsite resorts but if it's not available or I can get a room at BW or BC for less, I'll stay at one of those. I like the darker lobby and more adult feel of YC over BC, which tends to lean more toward kids. I also like the fact that other than one or two rooms, you are guaranteed a full balcony at YC where at BC you may end up with the little Juliette balcony. I like sitting on the balcony in the mornings with my coffee and watching the resort wake up and at night with a glass of wine and watching it go to sleep. BW is my least favorite of the three but I've only stayed in studios there so that might make a difference. I found the studio rooms to be a tad bit smaller than a regular resort room and it was before the recent renovations so they were definitely in need of some TLC. YC is getting ready for renovation but the last time I stayed there, last Sept., I had no problems with my room.
I didn't get to visit YC during our recent trip. Having balcony is a plus. Our upcoming trip is not until next summer. I currently have a room reserved at BwI with the BB booking as there is no availability at BC or YC. My parents will likely be going to WDW with us. I am a little worried that BWI might be too busy for their taste (I felt BW is busy from the pictures of the pool area... all that carnival thing). They might prefer something like BC or YC. But they also like the night time activities along the broad walk at BW.. Thank you for your feedback!!
BC and YC are basically the same resort, with lobbies separated by the restaurants.
Totally not the same resort. They are very near each other and do share a pool, but there are otherwise numerous important differences between the resorts, such as: (a) substantially all YC rooms have balconies, (b) BC lobby is usually quite loud, while the YC lobby is rarely so, (b) BC has a quick serve dining area, which YC does not, (d) YC quiet pool is actually in a location that is quiet (behind the building), while the BC quiet pool is just off the walking path around the lagoon, and (e) BC is closer to Epcot, YC is closer to HS (boat or walking).
That being said, I've stayed at each of YC, BC and BWI on multiple occasions. They are all great resorts and many wonderful amenities. So, to answer the OP's initial question, I don't believe that any one of those three resorts is substantially better than the others.
BC and YC are basically the same resort, with lobbies separated by the restaurants. Have stayed at both, and found whenever WDW is throwing around room discounts, YC is usually a better bargain (i.e. last time it was 30% of YC and 20% off BC, as BC is closer to Epcot). The only problem with YC from our last stay there was location. We were literally in one of the most remote rooms (first floor, facing the water, all the way closest to the bridge over to the Boardwalk area). It was quicker to walk over to the Swan and Dolphin and take boats from there! Also, YC doesn’t have a true quick serve dining area, so you had to traipse all the way over to the one in the BC, which was quite a hike to say the least.
We stayed in a similar location at YC (aka the other end of the world)! But we found walking outside by exiting from the stairwells made our walk to the lobby, pool, BC marketplace, or transportation a breeze. After we figured out this tip I would almost request this area again!
Another vote for the BWI. With the following caveat: If a pool is high on your list than BC or YC might be a better choice.
We like the BWI for the theming and have always had rooms overlooking quiet courtyards with Epcot in the distance.
We only spent a couple hours at the resort pool during our recent visit. I guess my family won't spend that much more during our next trip as we have waterparks and more option. It just seems to me that BWI is not as calm and peaceful as BC.. But I could be wrong as I have never step my foot at BWI and I could only make that assumption based on the pictures...