The whole bus sharing thing is way overdone. We have stayed at ASMusic twice and never had to share but also always were able to get a seat. There is a trade-off between sharing sometimes and having more frequent buses if you stay at the AS resorts (since you can take any AS bus). Pop also has 50 percent more rooms than each AS Resort, and each AS resort has its own front desk, concierge desk, gift shop and food court. Some people don't like how the food court at Pop is Combined with the store. There are also poolside movies at ASMusic which any AS guest can go to.
As for "newness" the rooms at both ASSports and ASMusic have been completely redone in the past couple of years, as have some of the common areas. So I would consider those the newest of the value resorts.
But...Pop definitely has a nice kiddie pool.
I would stay at any of the value resorts, but for now our favourite is ASMusic.