As far as I know (which isn't much, no expert!!), dogs are easier to train because they are used to living in packs and respond to an alpha figure (leader of the pack). Cats on the other hand, don't have a pack and live on their own or in small packs (like mother and daughter). Also, I know my cats could probably fend for themselves a lot easier than my dogs, so they also don't NEED to listen as well!!

Good luck with the assignment, have you searched internet as well, google always works well for me?