Having 3 kids in that teen age range I can think of at least 3 good reasons why YC/BC would be a great fit for your group.
First off you are within walking distance (5 plus minutes) to the international gate in Epcot, which is located between the countries of England and France. You are also a short boat ride away from Hollywood Studios. Both of these parks are teen favorites and I think you'll have more peace of mind if they decide to split up and explore the parks with out you. Teens at this age sometimes ask for more "off the family leash" time and having those two parks right there makes that much easier.
When going to AK or MK it's just a short bus ride away so that is just as accessible as though you were staying at any other resort.
The second reason would be the pool (Storm Along Bay or SAB) at the BC/YC. If you look at the layout on Google earth or even Robo's map
http://www.disboards.com/showpost.php?p=45719955&postcount=2 You will see there are lots of places that teens and adults can hang out and enjoy, like the lazy river for example. Storm Along Bay also has a long slide which older kids seem to prefer. SAB is not at all like those concrete ponds you find at other resorts.
Another reason is the access to all of the dining options at places like the Boardwalk or the countries in EPCOT.
If you stay at a MK area resort you'll have easy access to that park but if you stay at YC/BC you have easy access to two parks and the boardwalk area, more easily accessible dining options and a killer pool.
This is why my family decided to try the Beach Club with our teens.
A great place for comprehensive information about the Beach and Yacht clubs is located here.
http://www.disboards.com/showthread.php?t=2970473 This is a very welcoming group and it's where I found the best information to help make my decision. Feel free to join in the discussion with your questions about the resort. Be sure to read page one of the above thread link as it will answer MANY of your questions.
Good luck with your planning!
~NM
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