I have stayed at both ASMU and ASMO. You won't be dissappointed with Movies. It is great Disney atmosphere! If you have kids they will really enjoy it. We don't plan on staying anywhere else. As far as it being busier than Music... we were there Easter week (one of THE busiest times) and we didn't find that we were overwhelmed with people. We used the food court a lot and didn't have any problems finding tables, long lines, etc. We also found the bus service to be excellent, even at such a busy time.
Hope you have a great trip!