explain briefly the split between Snowball and Napoleon?

As the book unfolds both "leaders" are trying to assert their own power. Many of the arguments are really to impose their will rather that a real disagreement. Check out this quote from the book,

"These two disagreed at every point where disagreement was possible. If one of them suggested sowing a bigger acreage with barley, the other was certain to demand a bigger acreage of oats, and if one of them said that such and such a field was just right for cabbages, the other would declare that it was useless for anything except roots. Each had his own following, and there were some violent debates. At the Meetings Snowball often won over the majority by his brilliant speeches, but Napoleon was better at canvassing support for himself in between times. He was especially successful with the sheep..."