There would have been no debate about allowing slavery in the newly expanding territories and the South would have been under a tremendous financial and political strain in order to keep the institution of slavery viable. It would effectively make slavery illegal and ineffectual.
Freeing Dred Scot under the Gibbons rule would have ended the expansion of slavery into the newly formed territories since you could no longer transport slaves, either as property or as people. The courts would have had to address the use of slave labor to produce goods as well further crippling slavery. Had Scot been freed, John Brown would have never felt the need to use violence as a means to free slaves. Since the Fugitive Slave Act of 1850 would have been repealed, John Brown would not have needed to start and uprising at Harpers Ferry, and the resulting anger and fear that it caused would not have played a part in our nation going to