I'd say Jiraiya because he had much better chakra control than Naruto. Combined with his massive chakra supply he could probably use it more efficiently than Naruto.Whose Rasengan is the strongest? (simiple one)
- Naruto
- kakashi
- 4th hokage
- jiraiya
- konohamaru
Just because Minato created it doesn't mean his was better. The Rasengan is a technique that uses raw chakra to pump into a sphere. There is no hint that Minato had anywhere near the level of chakra that Jiraiya or Naruto hadMinato, he created it so he must have the stronger base rasengan