Persistent structures: Keep all versions, query any version.
Rollback Union-Find: Keep history stack, only access latest or rolled-back state.
| Persistent | Rollback | |
|---|---|---|
| Query any version | Yes | No |
| Space | ||
| Implementation | Complex | Simple |
| Path compression | No | No |
Use rollback when you only need to undo, not query arbitrary past states.
Use persistence when you need random access to version history.