Napoleon and Snowball do not make effective co-leaders. Snowball has greater leadership skills, but Napoleon is more ruthless.
As co-leaders, Snowball and Napoleon are at a stalemate. They do not get along, and when each contradicts the other it is hard to get things done. This results in division of the farm into factions, which is not healthy.
The animals formed themselves into two factions under the slogan, `Vote for Snowball and the three-day week' and `Vote for Napoleon and the full manger.' (ch 5)
As a leader, Snowball has good ideas and seems to really care about being democratic. He wants the animals to self-govern, and has them arrange themselves into committees. None of the projects were successful though. This allowed Napoleon to inch in.
Napoleon was a better leader than Snowball in the sense that he surrounded himself with advisors, delegated work, and consolidated his power. Almost from the beginning he took the puppies and trained them to be his security force. He used Squealer as his spokesman. He also began a campaign of misinformation about Snowball and eventually forced him out.
Napoleon was not a good leader because he was selfish. However, he was a more successful leader than Snowball because Snowball was incompetent.
Snowball would definitely be a better leader since he genuinely believes in true communism that Old Major believed in as well. Napoleon, on the other hand, had another aspect of communism in which he focused more towards the power that he and the pigs can gain.