It depends on how its programmed, but hopefully if all contacts are accounted for it shouldn't run any more sensor checks for suggestion two atleast. On the other hand with suggestion one, each DSTS you've got is running a check on every ship, and precipitating its own check from every other ship if they are on their own colony.
Another idea, if your problem is a bunch of freighters/colonies running everywhere, is to scrap them all, and fast OOB megafreighters/colonies of equal tonnage, but as just 1 ship, which should reduce some, or a great deal of the sensor checks being run.