There are millions of things
Napoleon is more of a demanding, overpowering pig who always gets what he wants. He gets influenced easily and always puts himself first. He believes that he is Animal Farm's destined leader and praises himself for all the things that he has done for the animals.
Snowball, however, believes in the happiness of his citizens. He would always put the farm first and try to achieve everyone's needs. For ex: before he was chased out, he drew diagrams of the windmill that would help the animals so they would work less. If Snowball was never chased out of the farm it would be at better state than it is at the end of the book
They both address leadership in different ways. Napoleon uses force, propaganda & slogans to get his way. While Snowball attempts to live accordingly to the ideology that Old Major has laid out for the animals . They are both inspired by this and they both want to gain the role of an ideal dictator. Both parties are corrupt whereas Snowball is a lessor evil.
