The main difference between evil eye and jinn... (i used to wonder about it loads and loads too) is that when jinns possess a person they make them turn away from the deen and anything to do with it- eg. Quran, Salah, Ghusl, seeking Knowlegde etc etc
But evil eye might make a person ill or suddenly become ill or harm to property because evil eye is a soul of the person affecting the soul of another person (or property) via envy and jealousy.
So evil eyes almost always has a physical symptom because evil eyes is done on things like beauty, valuable items.
Eg. Someone with envy says "That sister in pretty" and doesn't say masha Allah and maybe even hopes in her heart that something bad happens and then suddenly the poor girl gets spots or pimples etc...
Allah Knows Best