Really, this question is up to interpretation from each individual reader.  After finishing the novel and knowing what you know about Napoleon, how do you think it would have differed? 

We're told in chapter two that Snowball is better in speech and more inventive than Napoleon.  We know that Snowball prepared for and planned the building of the windwill in order to take some of the workload off the other animals.  It appears that Snowball is motivated more for the good of the farm why Napoleon is more interested in absolute control.  Perhaps with Snowball in charge, the pigs would not have become more human-like, but also, perhaps, they would not have made positive contact and relations with the human farmers neighboring. 

Although Snowball was a better thinker, he wasn't as menacing and ferocious as Napoleon.  It's difficult to say that Snowball could have forced the support of the other animals like Napoleon did; however, if Snowball could have continued to successfully defend the farm, it's more possible that Animal Farm would have operated more independantly than it does with Napoleon in charge.