Dear Student,
The difference between republican mahajanapada and monarchical mahajanapada are as follows :
1. Republican Mahajanpadas were ruled by a group of people elected by the common people whereas Monarchial Mahajanpadas were ruled by a hereditary King .
2. Republican Mahajanpada have a say in decision making because it was about the majority vote whereas in Monarchial Mahajanpada , the common people had little to no say in decision making as all the decision were taken by the King.
3. The Republics existed in the Indus Basin or in the foothills of Himalayan in Bihar or eastern UP whereas the monarchies existed in the Gangetic plains.
4. The Mahajanpadas of Panchal, Kamboj, Kuru, Vriji , Koliya, Bhagga, Licchavi, Shakhya were republicans whereas Mahajanpadas of Magadha, Kosala, Vatsa and Avanti were monarchies.
Regards.