I noticed when I returned to Detroit that some odd things had changed, but this was a very cursory look, so I don't know for sure:
- Broken walls were repaired.
- At least some computer terminals were un-hacked, even though I'd gotten every one available on the first run. Door panels were always still hacked.
- The available areas were slightly different - i.e. the police station was locked up the second time but a new area was available as part of the main quest.
- No new items seemed to be available in the areas common to both visits.
What, specifically, changes in Detroit and Heng Sha between the first and second visits to those locations?