what are two differences in how Northerners and Southerners viewed slavery

First, a disclaimer:  Northerners and Southerners are not homogeneous groups of people.  It would be possible to find a Southerner who objected to slavery just as easily as it would have been to find a Northerner who found nothing wrong with slavery.  That said, most Northerners were against slavery for various reasons.  Some disliked it on humanitarian grounds--this was especially true after the publication of Uncle Tom's Cabin which depicted slaves being whipped and beaten....

First, a disclaimer:  Northerners and Southerners are not homogeneous groups of people.  It would be possible to find a Southerner who objected to slavery just as easily as it would have been to find a Northerner who found nothing wrong with slavery.  That said, most Northerners were against slavery for various reasons.  Some disliked it on humanitarian grounds--this was especially true after the publication of Uncle Tom's Cabin which depicted slaves being whipped and beaten.  Some Northerners thought that slaves took jobs from people who could use them in the South and created a caste system of prominent aristocrats and poor whites.  Others believed that the 3/5 Compromise in the Constitution was unfair in that it granted states that had slaves extra power over states that only counted their citizens who could vote.  

Many Southerners believed that slavery was acceptable, if not good.  Many planters believed that they were assisting in civilizing their slaves and teaching them Christianity.  This paternalistic approach to slavery would also be echoed in European colonizing efforts in Africa and Asia.  They also pointed out that the Constitution did not allow for property confiscation and that the slaves if freed at once would face an uncertain future.  They pointed to the havoc of slave revolts, the most prominent of which was in Haiti in 1803.  Southern planters also argued that slavery allowed them to create the Cotton Kingdom which powered the world's textile industry--without slavery, workers in Britain and the northeastern United States would be unemployed.