What are the differences between Napoleon's and Snowball's behavior in Animal Farm?

In the initial characterization of the two, the author clearly draws a contrast between Snowball and Napoleon. He gives us insight into their general demeanor and personalities. This is obviously also an indication of how they would behave. The text states:

Pre-eminent among the pigs were two young boars named Snowball and Napoleon, whom Mr. Jones was breeding up for sale. Napoleon was a large, rather fierce-looking Berkshire boar, the only Berkshire on the farm, not much of a talker, but with a reputation for getting his own way. Snowball was a more vivacious pig than Napoleon, quicker in speech and more inventive, but was not considered to have the same depth of character. 

From these descriptions, it is clear that Napoleon was quite secretive and since he was 'fierce-looking,' one can assume that he intimidated the other animals. Snowball, on the other hand, was much more lively and a good speaker. He could generate ideas at a whim. The fact that he is described as not having the same depth of character as Napoleon suggests that he came across as somewhat shallow whilst Napoleon seemed to be a deep thinker. The significance of this contrast is expressed in the manner in which they later conducted affairs on the farm.  

Snowball was keen to educate the animals and adopted a practical approach. he tirelessly worked at creating a variety of committees so that tasks could be better organized. These, however, were a failure since the larger proportion of animals were not intelligent and could not completely relate to the purpose of Snowball's efforts. The reading and writing classes were, however, a great success.   

Napoleon, on the other hand, showed no interest in Snowball's activities. It was more important to him that the young should be educated rather than wasting time on teaching the older animals something new. Although Napoleon's approach seems to make sense initially, we discover that his motive for this approach was quite sinister. He took Jessie and Bluebell's puppies under his wing soon after they were weaned and kept them hidden. He assumed responsibility for their upbringing. Napoleon's purpose in this was not born from a generous desire to help but was informed by malicious and selfish intent. Once the puppies were grown, he used them to do his evil. At his command, they chased Snowball off the farm and executed animals during his bloodthirsty purge.

Napoleon's purpose in this was not born from a generous desire to help but was informed by malicious and selfish intent. Once the puppies were grown, he used them to do his evil. At his command, they chased Snowball off the farm and executed animals during his bloodthirsty purge. It is noticeably apparent that Napoleon realised that the young could be easily influenced and fed whatever propaganda he desired to. They could become tools and would be used as puppets in his hands.

Snowball noticeably made an effort to improve the lives of all the animals, whilst Napoleon was generally uninvolved. It was Snowball who had strategized to beat Mr. Jones and his men when they invaded the farm. He encouraged the animals and also spoke about them being prepared to sacrifice themselves for the benefit of others. Napoleon remained silent.

Napoleon's only real contribution after the Rebellion came from his opposition to all Snowball's ideas. Whilst Snowball won much support at meetings, Napoleon had in the interim taken to influence the sheep to disrupt him whenever it became clear that he was winning an argument as noted in the following excerpt:

At the Meetings Snowball often won over the majority by his brilliant speeches, but Napoleon was better at canvassing support for himself in between times. He was especially successful with the sheep. Of late the sheep had taken to bleating "Four legs good, two legs bad" both in and out of season, and they often interrupted the Meeting with this. It was noticed that they were especially liable to break into "Four legs good, two legs bad" at crucial moments in Snowball's speeches. 

It is obvious that Napoleon's actions were directed at serving himself, whereas Snowball acted in the general interest. This fact is pertinently illustrated by Napoleon's repeated rejection of Snowball's ideas. He, for example, urinated over Snowball's meticulous plans for a windmill.

Napoleon produced no schemes of his own, but said quietly that Snowball's would come to nothing, and seemed to be biding his time.

The difference in the two pigs' actions and thinking becomes plain in their disagreements about defence. Napoleon wanted to procure firearms for their own use whilst Snowball insisted that animals on other farms should be encouraged to rebel. Clearly, Napoleon's thinking was quite insular whilst Snowball displayed a wider perspective. Napoleon's selfishness comes to the fore when he finally has an opportunity to get rid of Snowball. At a time when Snowball wished to finally present his masterpiece (the windmill) Napoleon called upon his dogs to chase him off the farm. He barely escaped.

In the end, Napoleon became the tyrannical master of the farm. He claimed Snowball's ideas as his own and demonized him, using him as a scapegoat, in his absence, for everything that went wrong on the farm. Ultimately, Napoleon had become a much worse copy of the dictatorial Mr. Jones.