Diff Tools vs. Track Changes in Word: Different Workflows
A word processor's track-changes feature records edits as they happen in real time within a single ongoing document, making it well suited to active, collaborative editing where you want a running record of who changed what and when; a standalone diff tool instead compares two already-finished, separate versions of text after the fact, computing the difference retroactively — making it better suited to comparing two documents, drafts, or files that weren't actively tracked as changes happened, including text from entirely different sources or formats.
Both serve the general goal of "see what changed," but they're built around genuinely different workflows.
Where track changes is the natural choice
For a single document being actively edited and reviewed by one or more collaborators over time, track changes captures the full editing history as it happens, including who made each specific change — a capability a standalone diff tool, which only compares two static snapshots, doesn't have.
Where a standalone diff tool is the better fit
For comparing two versions that weren't actively tracked together — an old draft against a new one, text copied from two different sources, or content from two different file formats entirely — a diff tool can compute the comparison after the fact without needing any prior tracking setup, which track changes structurally can't do retroactively.