From the point of view of the inca people, what are some advantages of having an absolute ruler? what might be some disadvantages?

I think for the Inca people the advantages and disadvantages of absolute rulers would be very similar to the pros and cons of Absolutism in Europe. Some advantages: You have a strong ruler people can get behind which means less internal conflict and more stability. You also have someone who can make decisions, like war declarations, undisputedly. This means if instability provides a short-lived opportunity to strike, the Sapa Inca would not have to spend too much time gathering troops and gaining support for war. This strong, central government might have been marginally advantageous when trying to fight off the Spanish.

Some disadvantages are, like in Europe, limited powers to the people. Essentially the people are repressed and the rulers words are law. Because the Sapa Inca is ruling with divine right ( as with absolute rulers in Europe) his words would also seem to be what God is telling the people to do.