The main differences between agar jelly and gelatin jelly lie in their ingredients, texture, and setting properties. Agar is plant-based, derived from seaweed, making it suitable for vegans, and it has a firm, solid texture. In contrast, gelatin is animal-based, made from collagen, and offers a soft, jiggly texture. Additionally, agar sets at room temperature and is resistant to melting, while gelatin requires cooling to set and melts easily when the temperature rises.