Echoing what @Lycan-Thrope said — it is worth trying the GDI workaround before settling on the old Compare plugin, because that older plugin is no longer maintained and can develop incompatibilities with newer Notepad++ releases.
To try the fix suggested earlier in this thread: go to Settings > Preferences > MISC., find the rendering-mode drop-down (DirectWrite is the default), switch it to GDI, then fully restart Notepad++ and run the same comparison again. The crash appears tied to how ComparePlus draws its difference highlighting under DirectWrite, so GDI sidesteps it.
Two extra things worth checking if it still crashes:
Test with all other plugins removed, in case something else interacts with it (XML Tools was installed alongside ComparePlus in the original report here).
Check whether file size or shape matters — try a small pair of files first, then the large XML files, to see whether size plays a role.
If you get a chance, please report back whether the GDI switch helped. The plugin author said a reworked ComparePlus is on the way that should fix the DirectWrite problem, so a data point either way helps everyone following this thread.
