Overview
Rebase produces a cleaner linear history, but it rewrites existing commits and changes their identifiers.
When another developer has the original versions of those commits, the rebased branch no longer matches that developer's local history. Normal synchronization can then become difficult.
For that reason, rebase is presented as safe for local or personal branches where only one person is working, but risky on shared remote branches.
Merge preserves the visible fact that branches were combined. Rebase presents the work as a linear sequence. The choice is therefore not only about final file content; it is also about the history that collaborators will see and depend on.