IMO the best lounges were AKL and the GF (RPC). I've stayed in the 3 you are looking at, so I'll do my best to help you compare them:
BC -- lounge just ok (just a big room facing the parking lot), food nice but nothing "special", location of the resort and the pools there are a major factor in us choosing to stay there. I wouldn't pick it for the lounge, but we have added CL to our stay there and it was a nice thing to have. All the rooms ad lounge are on the 5th floor. Nice CMs. Added bonus: you can book the Sunrise Safari at AK if you stay CL.
AKL -- amazing lounge overlooking the lobby, so you get all the atmosphere of AKL. Large, spacious, really good food (different from any other CL), and the best espresso maker!!! Nice CMs. Great resort, animals, etc. A bit farther from all the parks though. Feels like you've been transported to Africa. CL rooms on the 4th floor with great savanna views, lounge is on the 6th floor so it's a bit of a walk to get there.
Poly -- big lounge with 2-story windows looking out to Bay Lake and the castle at the MK. Food pretty much the same as most places except the dinner appetizers were more poly-themed and quite nice. Can watch the fireworks from the lounge. All rooms in the Hawaii building (so you don't need to worry about which building you'll be put it), close to the lobby, close to the boat dock, and very close to the pools and beach. Great views from the TPV rooms there. Poly has the advantage of a boat or monorail to the MK, plus you can walk to the TTC to catch the monorail to Epcot, so it's a great location. Nice CMs.
All of them had helpful CMs. All were nice. I generally choose based on which hotel we feel like staying at at the time. AKL's lounge is my favorite of the 3, hands down, with Poly's lounge #2 and BC's #3. And we prefer the food offerings at AKL, too. But they are all nice and I don't think you will be unhappy with any of them.
Check out the CL thread, plus there is a CL-lounge photo thread -- that may help you get an idea about the lounges and the food they offer.
Hope this helps!
