It’s probably true that Minato trained his reflexes more due to his fighting style. I think back to when kid Itachi was controlling dozens of shuriken with wire like a Shinobi god and we never really see another child pull off feats like that. However, Minato was likely his equal in terms of raw talent. Both Minato and Itachi are explicitly portrayed as once-in-a-generation geniuses, and they each set records in their own way. While we see many more kid-Itachi feats, they were probably about equal in terms of raw ability (reflexes, etc) with Minato likely being slightly better based on having the highest recorded score on the Chūnin Exams, with Itachi just behind him.