In Preferences / IPTC/XMP, we get to specify the order in which embedded IPTC, embedded XMP, and XMP sidecar files are read. However, it doesn't seem to say anywhere what that means.
In particular -- is the first value for a field the one that the metadata screens show, or is it the last (in the order selected in preferences)? And is it per field, or overall? (I've seen various products over the years that use pretty much all possible permutations here, so no, it's not "obvious". Now, I might say that at least some of the weirder combinations are simply wrong, but I've still seen them.)