What are the similarities and differences between Merovingian dynasty and Carolingian dynasty?

The Merovingian and Carolingian dynasties were successions of rule by Frankish kings who united significant expanses of what we now call Europe. Kingship in both dynasties was hereditary, typically in the form of a son ascending the throne previously occupied by his father. Both partook in forms of the feudal system, where all of the land in the kingdom was divided up among the nobility in return for military service. The two dynasties shared many cultural similarities; they governed much of the same territories, practiced the same faith, and spoke Frankish dialects. Where they really differed was in the amount of power wielded by a king and how administration was used to manage the kingdom.

The Merovingian Dynasty was in power from 476 CE to 750 CE. Under the rule of Clovis I, most of Gaul was united as one kingdom.  When one Merovingian king died, his land was divided up among his sons. The sons ruled over their respective territories, but all were considered to be part of the same greater kingdom. Unfortunately, many of the Merovingian kings were more motivated by self-interest than by managing the kingdom. Instead, the Mayor of the Palace was responsible for managing the kingdom. By the time Pippin the Short deposed the last Merovingian king, they were essentially powerless figureheads. It was the weakened power of the Merovingian kings which gave way for the rise of the Carolingians.

The Carolingian dynasty (750 CE to 857 CE) had a similar system of administration for their massive expanses of land, which grew to include not only Gaul but also parts of Germany and Italy. The king would divide up land among his sons, but differed from the Merovingians by the fact that illegitimate sons could not inherit such territory. Under the rule of Charlemagne, the Empire was divided up into counties. Counts served as the administrative power for their territory and reported back to the king on an annual basis. Additionally, the coronation of Charlemagne by the Pope united the secular religious powers of Carolingian society. After the death of Charlemagne, division of the Empire served to weaken the kingdoms against the threat of invasion. Attacks by Vikings and a general disintegration of the unified power of the Carolingians eventually caused the Empire to collapse back into localized kingdoms.