Efficiency:- While open propellers are efficient for takeoff and initial climb once the aircraft reaches transonic speeds ducted fans are more efficient for propulsion.

Implementation:- Open propellers are easier to implement and weigh less than a ducted fan due to the lack of casing this lower weight could be critical where every gram counts.

Noise:- Ducted fans can control the noise created by the propellers specially at higher speeds.

Diameter Limitations:- Supersonic aircrafts typically require smaller diameter propulsive areas to reduce drag this is more easily achieved by ducted fans. Sophisticated inlet designs can also be done only by ducted fans not open propellers.

Motor Integration:- Ducted fans allow for better integration with the electric motor possibly reducing overall complexity.

Safety:- Ducted fans offer better containment incase of failure specially at supersonic speeds.

Ducted fans are superior to open propellers theoretically but are harder to implement and design for specially for a first prototype for a startup. Ducted fans will also likely require longer runways compared to open propellers an important constraint to keep in mind. Perhaps a compromise between the two is possible.