In the past digikam overwrote all the elements from darktable when saving its content into XMP files. if that bug is fixed. it should probably work to use the same XMP for both. If it isnt fixed yet, we should really push the devs to finally fix it 
In the past digikam overwrote all the elements from darktable when saving its content into XMP files. if that bug is fixed. it should probably work to use the same XMP for both. If it isnt fixed yet, we should really push the devs to finally fix it