Both during the battle and also before it, Snowball shows his capabilities as a military leader, strengths which extend beyond his battlefield exploits into the areas of preparation and erudition. This we see in his studies of Julius Caesar. In these preparations, we also get a sense of pragmatism on Snowball's part, given Snowball's willingness to learn from human example regardless of Animalism's hostility towards the human species. During the battle itself, he shows his courage and fortitude, leading the animals to victory even as he is wounded in the battle.
While Boxer shows his strength (being the strongest of the animals on the farm), he also reveals his kindly and well-meaning nature. During the battle, Boxer believes he has killed one of the humans, an act which causes him sorrow. This attitude is in stark contrast with Snowball's own ruthless and militaristic pragmatism. While the other animals are celebrating their victory, Boxer is concerned with the life he thinks he has ended.
Finally, Mollie flees the battle entirely and is later found hiding. Keep in mind here that, unlike so many of the other animals, Mollie is depicted as having preferred life as it had been before the Rebellion and thus does not have the same stake in its continued success. Thus, in this scene where the farm comes under attack, we see her refusing to come to its defense. Later, in chapter 5, we'll find Mollie fleeing the farm to return to life under human control.