Some advantage of a monarchy democracy is that there is only one person making the decisions so it gets done faster. Another is that the people don't have to worry about elections because the ruler will pick the next.
Some disadvantages of a monarchy democracy is a single person will run the country as long as they live.
Some advantages of a dictatorship is that there are very low crime rates. Another is that there is very fast progression in the country.
Some disadvantages of a dictatorship is that it is prone to collapse because people get sick of the rulers extreme rules. Another is people are killed for even the smallest crimes so people end up dying all to often.