I believe that more detail is needed in order to compose this speech. One specific detail that is needed would be when this speech is given. Is it at a point where Napoleon and Snowball share power, such as the building of the windmill? Is it at a point where Snowball has been branded as an enemy of the farm? This is critical to establish.
If all things were considered equal, I think that the voting for either candidate would be dependent on what was valued. If the voters were asked to place importance on the belief in the revolution, Snowball is the obvious choice. This argument rests on how Snowball never wavered in his commitment to the revolution and to Animalism. His following of the commandments was evident in all that he did and demonstrated. Snowball was the most zealous in talking to the animals about Animalism and the impact it has on their lives and the farm, in general. His intelligence regarding how to make the theory of the revolution into a reality is where voters would make their decision.
If the voters were asked to vote out of who is a better leader in terms of understanding the needs and demands of authority, the vote would have to go to Napoleon. Napoleon proves himself to be the ultimate in leaders. From the very first moments that the pigs have power, Napoleon is concered about leadership and how to maximize it. Theory is secondary to practice for Napoleon. The rearing of the pups into his security force is one such example. The ability to assert unquestioned control on the farm would be another example. While he is despicable in what he does, there is little argument as to who is the unquestioned leader of Animal Farm/ Manor Farm. One does not have to go far in recognizing who is able to embrace the demands of leadership and embody it. It is Napoleon, and I think voters would be persuaded by this. Certainly, the animals the story are persuaded, in varied ways, of this quality within Napoleon.