Some differences I’ve found on iOS:
- JS scrolling doesn’t work on embedded iframes, while overflow scrolling does.
- WIth overflow scrolling, when tapping an item (e.g. a button) while scrolling, the event and highlighting (active state) may be registered on the wrong item.
- The behaviour when the keyboard opens may be different.
- Overflow scrolling is more affected by Safari bugs, e.g. scrolling in the wrong direction or hanging in some edge cases.