CompareAssemblyInstances gives incomplete information. It is very cumbersome to determine it. Please update API for more details as below:
1. AssemblyDifferenceMemberCount should also provide element ids those are extra. So it helps user to isolate or select and act on them.
2. AssemblyMemberDifferentParameters should also provide list parameters / values those are different.
3. AssemblyMemberDifferentGeometry should also provide list geometry references like face, edge etc those are different.