Snowball is a planner and he keeps no secrets. He designs and implements plans that fit with his political views. Some of these plans work and some of them do not work, but all are fully on display and in the open.
For instance, the "Battle of the Cowshed" is an example of one of Snowball's strategies/plans that worked to near perfection. The animals successfully drove off the human attack and defended Animal Farm.
Snowball's other plans don't work as well, such as his many committees and his windmill plan. Though Snowball does not have a chance to see through his plan for building the windmill, there is evidence to suggest that it would have been impossible for the windmill to achieve all the many things that Snowball hoped it would.
When the windmill was finally built, it did not produce electricty, but instead ground corn.
Snowball's enthusiasm is one of his central traits, despite the occassional failure of his plans, and it is this enthusiasm that distinguishes Snowball from Napoleon.
Napoleon has no plans for the farm with the exception of plans to gain increasing levels of power and priviledge for himself. Napoleon's cynicism, conniving, and secrecy are perhaps most clearly exemplified in the act of chasing Snowball off the farm.
The dogs were kept as one of Napoleon's secrets and are brought out in a surprise attack meant only to secure Napoleon's place as leader. There is nothing at all good for the other animals in the act of Snowball being chased away.
...Napoleon seems to embody the idea that with power comes corruption.
Snowball's ideas, however farfetched, were always intended to perpetuate his political ideals and to better the lives of the animals on the farm. Napoleon, on the contrary, has ideas only to serve himself. He is dishonest and secretive where Snowball was neither of these.