I had a friend come visit from out of town and we hit several of the Memphis attractions. We decided to check out this museum nearly immediately after visiting Sun Studio. There is no comparison. Sun Studio has a fabulous guided tour which takes you chronologically through the amazing history of the establishment. It is quite a small place, but all very well preserved and intact and you get the feeling you're standing next to the recording artists as they are performing their first recordings. Everything at Sun feels so genuine and puts the location you are at into a very apparent historical context.
Stax, on the other hand, felt like a renovated new space with little historical significance to the museum space itself. The tour began with a video that felt a bit PBS documentary-like about soul music. Then the tour of the museum artifacts was self guided and not particularly gripping. I did not feel that the museum put soul music into a good historical context and chronologically it was very hard to follow. Basically, it lacked a compelling story.