In the book Animal Farm, what is Napoleon's and Snowball's point of view on the defense of the farm?

Napoleon and Snowball have a radically different understanding of what the pigs' control of the farm should mean. Snowball is more idealistic; he genuinely believes in the political principle of "Animalism" (read: Communism). He's more intelligent than Napoleon; he's also a much more sophisticated thinker and a much better orator, skillfully using his rhetorical power to convince the other animals of the benefits of Animalism.
Snowball wants to defend Manor Farm by spreading revolution to other farms. The more widely the Animalist rebellion spreads, the more difficult it will be for the human enemy to fight back. He is somewhat idealistic but does at least appear to have a genuine belief in his political creed.
This is more than can be said for Napoleon. He sees Animalism as a means to achieve absolute power. He is profoundly jealous of Snowball and sees him as a threat to his plans for dictatorship. He's deeply resentful of the fact that Snowball is much more popular with the farm animals; he also has a chip on his shoulder about his own relative ignorance and lack of sophistication.
Napoleon isn't interested in defending the revolution by spreading it beyond the confines of Manor Farm. Doing so would undermine his power while increasing the power of Snowball. So long as there is a revolution in one farm, he can maintain control over the animals.
The characters of Napoleon and Snowball are based respectively upon Stalin and Trotsky. Their rival conceptions of Animalism also reflect the differences between Stalinist "Socialism in one country" and Trotskyist "Permanent world revolution."