id say it is debatable. The Juubi at the time before his death was sealed within him, and if he died without passing it on or splitting it, then it would be released to rampage the ninja world. However, the decision of splitting it may have made it more managable for his sons and the future generations in the sense that it was easier for them to control them rather than to face off against the Juubi. And since he chose to split them, it might of been because he did not believe that his sons could handle it. Other than that, they were split for other reasons, one may be to help create peace across the ninja world and stabilize it, at least thats the vision that Hashirama later had.