Refer to the release notes
At high level, there are lot of new features related to e360 , provisioning tool capabilities to build e360 application,task management and SAM integration for e360(for more details please refer release notes)
10.3 release will have more enhancement and bug fixes which may not be available in 10.2. Please refer MDM Release Guide which can exactly answer what you are looking for.
Some functionalities not are still not available as part of BE but were available in SA are -
- Mapping is not exposed as Business Entity object so any CleansePut will not work in BE architcture.
- Update and Add HM Relationship Handler User Exit is not present in new design.
- MergeHandler does not get called from Task Context.
- Merge Preview screen is still not having functionalities of Legacy Match screens. Like select all, Unselect of the merge candidate from Task etc.
- Bulk Import
Hopefully this helps somewhat.
apart from the previous comments, there are a lot of bugs fixes in MDM 10.3 and there are many enhancement included in MDM 10.3 when compared to 10.2 version.
All the Jira details are mentioned in the release notes of MDM 10.3