Napoleon and Snowball are two leaders with very different personalities, as is clear from the following introductory description.
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.(chapter 2)
Napoleon, then, is big, tough, ponderous, and laconic while Snowball is quick, fiery and talkative. However, from this description, we get the sense that ultimately Napoleon's is the more powerful and forceful personality, and so it proves.
In their clash of temperament, outlook, and ideas, it is inevitable that the two pigs should become rivals. Although to begin with Snowball appears to be the more successful and charismatic leader, with his fine powers of speech, organisational abilities and passionate idealism, he is eventually outmanoeuvred by the cunning and ruthless Napoleon. Napoleon is more interested than Snowball in obtaining personal power and stops at nothing to achieve it. While Snowball has the popular touch, Napoleon is content to work behind the scenes, and finally emerges with supreme power.
The power struggle between Napoleon and Snowball is deliberately reminiscent of the rivalry between Josef Stalin and Leon Trotsky in the early days of Communist Russia. Napoleon, in his laconic brutality and scheming ways, resembles Stalin while Snowball resembles the brilliant and energetic Trotsky. Just as Stalin finally ousted Trotsky, and proclaimed him an enemy of the Communist state, Napoleon eventually expels Snowball from the farm by brute force and blackens his very memory thereafter.
When compared to Napoleon, Snowball certainly is the more appealing character. However, while not ruthless like Napoleon, he too is seen to have his faults: he is quick enough to assume the pigs' superiority over the other animals at the start, and he has a tendency to somewhat idealistic and impractical schemes, like the windmill, which he stubbornly insists on pursuing.