Same result. Instead of telling them to repent in order to receive benefit; the Lord foretold of their imminent doom, thus causing them to repent.-------------------------
Everyone has opinion.
Jonah was NOT telling them to repent....he was proclaiming Jehovah's JUDGMENT- which CHANGED when they repented.
Had Jonah gone in and told the Ninevite's to repent of their actions, to which they were unaware of doing wrong, they would have merely ignored Jonah at best.
Jonah 4:11 And should not I spare Nineveh, that great city, wherein are more than sixscore thousand persons that cannot discern between their right hand and their left hand; and also much cattle?