I could be wrong here, but since 2 potentially matches to a much smaller number of records, there likely will be a much smaller set of records to "filter" which may create a noticeable difference if you have a large number of records in the portal's data source table. I haven't run any test or experiments so could be wrong here.
You can also use:
Cu_Main::anyfield X CU_invLine4DKUSearch
as your first relationship. The X operator is a "match all values operator" that can be used in place of fields like AlwaysTrue.