With a bunch of separate files, you can at least open two of them quickly and do a manual scan, but with git you can only ever have one version checked out at the same time, so now you’ll be checking out an older version, making a temporary copy of that, and then checking out the version you want to compare it to and STILL end up doing just that.

What? I don't understand what are you trying to say. Are you trying to do manual scan of xml inside? It's useless, internal format is not intended to be human-readable. But you can use regular git diff anyway.

Or if you want to compare rendered documents, then you probably need to make git diff driver. Or checkout multiple worktrees and use libreoffice's comparasion.