I think Minato's was greater.They both saved the whole village and prevented war but Itachi left a survivor that is now threatening the village. Although this was a selfless act, it brought about a negative outcome. Minato on the other hand, unlike haters who say he was being selfish by trying to make his son a hero....... sacrificed his only son to save the village. Yes, Minato wanted him to be thought of as a hero, but not in a selfish way. I'm not a Minato fan boy, seeing as I like the Itachi story more than the Minato one, but if you look at the facts, Minato's sacrifice was a little better... That's my opinion...