The utlrp.sql compiles all invalid objects in the whole database.
The other script works in a more specific manner. The following lines are at the header of the adutlrcmp.sql script:
rem - compiles any invalid APPS_DDL or APPS_ARRAY_DDL packages
rem (in the whole DB, not just in the current schema)
rem - determines what objects are invalid in schema_to_compile
rem - determines the dependencies between the invalid objects
rem - assigns each invalid object to a logical worker for compilation
The adadmin passes the APPS schema as a parameter and therefore the script compiles the APPS schema plus the two packages mentioned above and all dependent invalid objects.