Both, Leeches and Slugs are elongated-slimy creatures, but vary in their habitats. Leeches are relatives of earthworms, and mostly feed upon blood of other creatures, whereas Slugs belongs to Mollusks, hence...

Earthworms and Leeches are hermaphrodites, but differ in their subclasses; Earthworms fall under sub class Oligochaeta, whereas Leeches fall under Hirudinae.