Answer First of all, there will be a major difference in the air temperature from the supply registers.
Heat pumps, regardless of the type, produce lower temperature air than fossil fuel furnaces.
Another issue is the ductwork. If the house was not originally equipped for air conditioning, the ductwork may be undersized for the heat pump. Both central air conditioning and heat pumps require more air flow than fossil fuel furnaces. Be sure to have your contractor evaluate this issue. Undersized ductwork results in noise and lower system efficiency.