Answer:
The advantage is that there would be no disagreement among the House, the Senate and the Presidency. So all decisions would be unanimous, therefore there would be less time-consuming deberation.
Step-by-step explanation:
The disadvantage with this state of affairs would be that there would not really be representation of citizens´ points of view, nor from other parties. So all the affairs of the nation would be in hands of people of only one political preference.