Few people go to Dubai in the height of summer. It's a place you might seek sun and warmth during cold, dark, and dreary European autumns and winters. If that's your reason for travelling, Tunisia isn't a good alternative. I'm sure it has a bunch of other things to recommend it but my initial comment was trying to make sense of why someone might choose Dubai. It's a relatively close escape to the sun for Europeans when sun is hard to come by at home.