deshou is usually used to express an uncertain affirmation, but it also works as a reminder, like: "but weren't you afraid of dogs?" desune is just used as a normal question in which the speaker thinks the other person is afraid of dogs: "you are afraid of dogs, aren't you?"

Deshou でしょう is a ultra polite form of だろう darou.

"inu ga kowai no deshou?" and "inu ga kowai no desune" are almost same meaning. "deshou" sounds softer than "desune".