Hi,
Some of my observations are below.
1) In Core services there is a limitation in size of file that can be uploaded in customer attribute if you want to create audience based on offline attributes ( i guess it is 100 MB) but if you have large data file AAM is preferred option
2) Limited options in real time analytics audience to create complex segment with analytics data however it is feasible to create complex audience based on analytics data in AAM.
3) Segments created in core services do not do cross device profile link which AAM does