I have the same questions. We are booked for the ASmo this April. It will be our first visit. I had considered doing POP too. I went with ASmo after much research. For me, the Buzz section would be heaven for DS. I figure that if the buses get backed up, they can let dispatch know, so that will be okay. My SIL has stayed at POP and really liked it too. I think they are similar, but I have read POP does standard soap where ASmo uses mickey shaped soap that isn't the best (solution, just bring your own). The POP according to the UG has a pop up play water area for younger kids and I don't think the ASmo does. I understand both properties (all all stars combined & pop) to be similar in size. The only question is if POP may be 1/2 the size as only phase 1 is open.
I feel for you. Right there with you in the planning. For me, the movies would be much more exciting to DS than POP, although he wouldn't know what he was missing if we stayed at POP, but I would. ha. The things we do for kids! If you do go with POP be careful about what building you pick. I've heard some are right along the highway and noise can be more of an issue. As someone else said, try to do preferred. I think that will keep you central to food & bus stops and by defalt the highway.
I have heard that the ASmo are very soundproof. I wouldn't see why the POP wouldn't be too since it is a newer property.
Hope this has helped some!