What is the difference between Spongocoel and Coelenteron?

Hint: The gastrovascular system cavity of coelenterates is extensively branched into a system of canals and is commonly known as a "blind gut" or "blind sac". It serves as a common opening for entry of food and excretion. A spongocoel is the large, central cavity found in sponges. Based on the complexity of a sponge’s body plan, the sponge can have simple interior space or a complex branched inner structure.

Complete answer:
Phylum Coelenterata has a central cavity called coelenterates which helps in digestion and circulation of food. The other name of coelenterates is a gastrovascular cavity.
Phylum Porifera has a peculiar canal system whose central cavity is known as spongocoel. The other name of spongocoel is paragastric cavity.

Additional information:
Peculiar features of phylum Porifera
> Presence of two pores-Ostia and oscula
> Presence of the canal system
> Presence of choanocyte or collar cells
>Endoskeleton is formed of spicules or spongin
> Presence of spongocoel.
Peculiar features of phylum coelenterata
> Tissue level of organization.
> Incomplete gut
> Presence of cnidoblasts for defence and offence.
> Presence of the diffused type nervous system.

Note:
Coelenterates shows progress in evolutionary terms over sponges that are lined by gastrodermis.
Coelenterates has only one aperture mouth, so the anus is absent. Spongocoel found in sponges are lined with choanocytes, where flagella beat to maintain water current and pushes water through the spongocoel. The entry of water in the spongocoel takes place through Ostia and exits through the osculum.