Final answer:
Galactic cannibalism involves a larger galaxy absorbing a smaller one and typically results in a massive galaxy, while merging galaxies involve galaxies of equal size combining to form a new galaxy.
Step-by-step explanation:
The difference between galactic cannibalism and merging galaxies lies in the size of the interacting galaxies and the outcome of the collision. Galactic cannibalism is a process where a larger galaxy strips material from, or completely swallows, a smaller one. This often occurs in rich clusters, leading to the creation of a massive galaxy. On the other hand, a galaxy merger typically involves two galaxies of comparable size that collide and coalesce, which can occur in both rich and poor clusters and creates a new galaxy that is a combination of the two original galaxies.