It was stated several times that he inherited more from his mother than father.
But wasn't that just his personality? he has his mother's temper, round face, and doesn't do well with school work, and is very rowdy. Kushina was all those things. But I don't think it was ever said anything about him inheriting more of her genes than Minato.
The Uzuamki is slowly being diluted, as someone said. The red hair seemed to be getting recessive, or may be with women. Then the life-force is dying down as well. Kushin survived an extraction and just giving birth, and still had enough strength to get to the battle field, and stop Kurama from stabbing baby Naruto .But Naruto lost Kurama, and was on the verge of death, with Sakura having to manually pump his heart. Then Naruto has alot of chakra. But does it have the potency of an Uzumaki? because Mito and Kushina could keep Kurama in check. Naruto had to have outside seals used to keep Kurama under control.
Karin seems to be one of the last few pure Uzumaki. otherwise, there's probably some descendants and diluted members left.