All Star Music has a beautiful little rose garden with a fountain by Jazz Inn that we love. The Calypso buildings (preferred rooms) are the most convenient to the food court and buses, so if preferred is in the budget, I would recommend staying in one of those. The resort is spread out so that some of the furthest rooms are a bit distant. ASMu is the middle of the three AS resorts, so when buses are shared it is the second stop.
For an adults only trip, it is my favourite AS resort. ASSp is perhaps slightly better laid out and has the first bus stop, but you can always walk across to there if you would like.
There is no huge difference between the three AS resorts except the theming, really. ASMu has a really nice theme and we have always enjoyed the food court there.
Enjoy your stay!!!