I don't really think this represent different options.[:)]
This is actually a difference between two internal field names: "crossref" and "xref", so they are actually different options.
Unfortunately, I don't know offhand if there is a semantic difference between these two internal field names, or if they are just two names for the same concept, and should be unified.
AFAICT, only "TISCHCAPP" (LLS:29.3.11) uses the 'xref' field, so it may be a problem isolated to only this one resource.
