Naruto would win.
Naruto's sensor and perception abilities surpass Minato's by far.
Minato's only good quality's are intelligence and speed.
Intelligence is what makes him so dangerous and his speed applies intelligence.
So Minato can use his speed for attacks such as Rasengan.
But one big factor here is that Minato's speed is only capable due to his reaction time.
Naruto in SM has reaction time much faster than Minato due to his Nature affinity.
He can sense and react to an attack faster than anybody. He dodged a super speed attack coming from the 3rd Raikage in SM without super speed that he has in KM.
So Minato can not do much if he can not hit him.
Whilst Naruto has many ways of hitting him since Minato does not have knowledge of his SM. One punch from Naruto in SM and Minato is out. Not to mention Rasenshuriken, Summons, Clones (which Minato can not tell the difference), and his seen ability to come up with plans for a win in crap situations.
Naruto wins Mid-Hard diff.
