Question: Differences between RAW and sidecar xmp

[Uwe]

Hello, when I started shooting in RAW format, about 20 years ago, I had written the metadata to the RAW file. But I stopped doing that a long time ago and now only use xmp sidecar files for the metadata. How should I deal with the status of the "old" RAW files that the IMatch metadata analyst shows me the existing differences between XMP/IPTC between RAW and xmp sidecar? Should I use the ExifTool command (exiftool -xmp= -itpc=) to delete the metadata in the RAW files?
regards, Uwe

[Mario]

By convention, RAW files use XMP in sidecar files. This is the most portable approach.
Native EXIF, GPS and legacy IPTC (IIM3) metadata is stored in the image itself. XMP contains copies of EXIF, IPTC and GPS tags, so when you change one of these tags (date and time, description, GPS coordinates) that these changes are done in both the XMP and the native metadata embedded in the image.

IMatch takes care for that. Many software out there does not or does a half-assed job.

When IMatch imports your image, it detects the XMP sidecar file (if there is one), XMP metadata embedded in the image, EXIF, IPTC and GPS metadata. From that it produces a "super" XMP record, mapping native metadata into their XMP counterparts.
When you write back, IMatch writes XMP into the sidecar file (not to the RAW!) and updates EXIF/IPTC/GPS in the RAW, when the data exists.

Having two sources of truth (XMP in the RAW and XMP in a sidecar) is never good.
IMatch updates XMP in the sidecar file.

Removing the XMP record from the image is the best approach. There is a preset for that available in the ExifTool Command Processor. You can keep the legacy IPTC record, if you need it for some reason (unlikely, unless you exchange RAW images with clients or services which rely on legacy IPTC metadata). IMatch updates the legacy IPTC data in the RAW when it writes back changes to keep IPTC and XMP in-sync.