The difference between Snowball and Napoleon becomes more obvious in Chapter 3, where both are showing signs of their personal ideology. Snowball, an idealist, truly believes in the teachings of Old Major and he concerns himself with education and promotion of ideals; Snowball's focus is on making life better for the animals by utilization of Old Major's philosophy. Napoleon, by contrast, is already working on his power grab, and like all dictators, he understands that children are his best bet for indoctrination:
Napoleon took no interest in Snowball's committees. He said that the education of the young was more important than anything that could be done for those who were already grown up.
(Orwell, Animal Farm, msxnet.org)
Although only the dogs are mentioned specifically, it can be inferred that each new generation of animal is indoctrinated in similar ways. Since animals have more babies than humans, and more frequently, the changeover between the old animals who lived through the Revolution and the new generation who never knew anything different was fast. Showing this subtle difference informs the reader that Napoleon is heading directly for a no-tolerance policy of suppression, rather than a society of equality. Snowball, with his idealist thinking, would have led the animals into a truly Utopian society, but he was doomed from the start as he didn't have the sense to create a power-base for himself.
I think that there are some distinct significances in how Orwell creates divergence between Napoleon and Snowball. Snowball is more concerned with continuing the spirit of revolution. He does this by seeking to organize the animals into committees to divide work and speaking with them in a way through which they understand that the revolution still lives and lives within them. Napoleon is more concerned about power and ensuring that he possesses it. Taking the pups and raising them for what will become his secret police is reflective of this. The significance of Orwell bringing both divergent realities out is to make clear that there is a difference between seeking political control and keeping it. Snowball's vocabulary and pattern of recognition is one in which the revolution's spirit is ongoing. Napoleon views reality in a sense where power is the only reductive element. The idea here is that demonstrating their difference reflects how political action looks different between struggling for independence and maintaining power. It is here where I think that the significance is most evident in bringing out the differences between Snowball and Napoleon.