Snowball is a schemer. There is no telling what projects beyond the windmill he may have inspired the animals to pursue. The question remains just how practical his projects would have been. Like his many committees, his projects may have come to nothing. So, the farm may have been busier if Snowball had been the sole leader, but not necessarily more productive.
It's tempting to suggest that Snowball would not have declined into such despotism like Napoleon, but there is no real evidence to support this inclination. Snowball ate the apples and was willing to accept special treatment, a trait that, in Napoleon, led to thorough corruption.
Unfortunately, if the theme of the novella is that power corrupts and absolute power corrupts absolutely, the conclusion is inevitable--no matter who is in power. Though the end is probably inevitable, the process would probably have been slower if Snowball had been leader of the farm instead of Napoleon; and perhaps the carnage would have been less. In the end, however, Snowball would have had to take many of the same drastic measures and use the same propaganda as Napoleon in order to keep his position of power.
It is an interesting question. I think that there might be two different approaches to answering it. The answer that contains the most amount of hope would suggest that Snowball always viewed leadership on the farm from a different point of view than Napoleon. For example, in chapter 3, Napoleon is focused on taking the puppies and raising them for his own. He understands from an early point on that his political control is going to rest with development his own enforcement wing that will guarantee his rule not be threatened. At the same time, Snowball is taking animals and teaching them how to read, as well as developing committees to increase production. This difference reflects how Snowball views leadership as one that benefits the farm, and how Napoleon views it, as a political means to extend his control. In this difference, one might be able to assert that Snowball has a more communitarian vision of leadership, one that is more empowering and probably more theoretically true to Old Major's vision than what Napoleon has in mind.
The second way of viewing this difference is a more bleak one. This reality suggests that the overall theme of the work is that power corrupts and the more one has power, the greater the propensity one has for corruption. Snowball's assertion of power would simply be another reality in which those in the position of power act in a corrupt manner that is antithetical to the needs of the greater good. The reality is that while leaders profess to act in this name, their actions speak towards acting in a self- interested manner where consolidation of their power is the most important element. If one accepts the ending of the work and the themes that arise from it, there is no difference whether Snowball or Napoleon is leader, as corruption is the end result in both settings.