th diffrence maybe with how naruto used the oil. others only dabbed a little bit on when they first started and naruto jumped in. the amount of oil used may have changed the rate of his training.
or it could be due to his chakra already naturally mixing with kyuubi. seeing as all other nin only have one kind of chakra, when they woud use sahe training the would be the first time their chakrea has had to mix with anything else but since naruto's body has been natually mixing its chakra with an outside source for so long maybe his body naturally allows him to absorb other means of energy considering it absorbs the kyuubi chakra on a daily basis.
or it could be narutos drive and will. if you think about it jiraiya never had the drive naruto did to master it. jiraiya never needed sage mode so he never really saw a point in mastering it sseing as he could summon any toad he needed including the two frog sages so he never had to master it, especially when ma and pa would help him with it anyway. and jiraiya wasnt the most focused nin. his mind was always wondering so he never really consentraited on one thing. think about it, he was always worried about what orochimaru was doing, then he was always writing a new book, trying to figure out why minato sealed th kyuubi in naruto, questioning himself, wondering about women, blaming himself for minato and later sandaimes deaths, blaming himself for not stopping orochimaru. jirayia never could foucus on training, hell he never even fully focused on his fights.
when he was fighting orochimaru he got caught of guard paying attention to naruto, when he was fighting pain ma and pa did most of the thinking for him. had it not been for ma and pa being there jirayai would have died much sooner sage mode or not because he was horrible at focusing on any one thing.
thats what made narutos training much easier. dispite him not being as smart as other characters his drive and his one track mind help him more than anything. because he is able to focus on one thing for so long he is bound to figure out anything he thinks about eventually. this does not make him a genius, just very motivated and driven