Advantages of the democratic system would be:
1.President is directly elected by the people; which makes him more responsive to the people.
2.Separates executive and legislative powers; allows each branch to watch the other branches to prevent any abuse of power.
3. Fixed terms allows more STABLE system.
Advantages of a monarchy system would be:
1. Decisions are carried out on his word alone (no fighting or bickering)
2. Clear line of succession
3. Can inspire GREAT loyalty among the people, creating a strong bond to hold a nation together.
Hope this helps :)