Napoleon is sneaky. He helps redirect the animals' attention. This will be a consistent theme throughout the book so it is good to look at here. At one point, the milk and apples go missing. Napoleon said, "Nevermind the milk... that will be attended to."
I would also point out that Napoleon is cowardly. He did not put himself out there as any kind of major player in the Battle of Cowshed.
Napoleon also bides his time. Snowball was creating plans, and Napoleon is often referred to as quietly asserting that Snowball's plans wouldn't work. That also makes him someone who will betray.
Snowball has great ideas, he wants to unify and educate the animals. Snowball acts with great bravery and courage going into the Battle of Cowshed with great strategy and self-sacrifice.